Black Box Modem MD1640A User Manual

AUGUST 2000  
MD1640A  
MD1641A  
Series II Modem 336  
Series II Modem 336+  
CUSTOMER  
SUPPORT  
INFORMATION  
Order toll-free in the U.S.: Call 7877-877-BBOX (outside the U.S. call 724-746-5500)  
FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746  
Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018  
Web site: www.blackbox.com  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
DISCLAIMER  
This publication may not be reproduced, in whole or in part, without prior  
expressed written permission from the manufacturer. The manufacturer  
makes no representations or warranties with respect to the contents hereof  
and specifically disclaims any implied warranties of merchantability or fitness  
for any particular purpose. The manufacturer reserves the right to revise this  
publication and to make changes from time to time in the content hereof  
without obligation of the manufacturer to notify any person or organization  
of such revisions or changes.  
TRADEMARKS USED IN THIS MANUAL  
MNP and Microcom Network Protocol are trademarks of Microcom Inc.  
AS/400 and System3x are registered trademarks of IBM.  
Appletalk, Mac, and Macintosh are registered trademarks of Apple  
Computer Inc.  
Unix is a registered trademark of X/Open Co. Ltd.  
Microsoft and Windows are registered trademarks of Microsoft Corporation.  
All other trademarks mentioned in this manual are the property of their  
respective owners.  
2
 
Table of Contents  
Contents  
Chapter 1 - Introduction and Description  
1.1  
1.2  
1.3  
1.4  
1.5  
1.6  
1.7  
1.8  
1.9  
Introduction............................................................................7  
How To Use This Manual ......................................................7  
What is in Your Modem Package? ......................................10  
Modem Features ..................................................................10  
Fax Features ..........................................................................11  
Technical Specifications ......................................................12  
Power ....................................................................................16  
Modem LED Indicators ......................................................16  
Controls on PC Board..........................................................18  
Chapter 2 - Installation and Connection  
2.1  
2.2  
2.3  
2.4  
Safety Warnings ....................................................................19  
Installation ............................................................................20  
Is Your Series II Modem Ready for Use? ............................23  
Operating Your Series II Modem ......................................24  
2.4.1  
Simple Operations ......................................................25  
2.5  
The Answer/Originate - Voice/Data Toggle Switch..........25  
Chapter 3 - Software Configuration  
3.1  
3.2  
Introduction ........................................................................26  
Serial Port Limitations ........................................................26  
3.2.1  
3.2.2  
How Can You Identify Your UART Type?....................27  
The 16550 UART and Windows 3.1 ............................28  
3.3  
3.4  
Configuring Your Software ..................................................29  
3.3.1  
Configuring Software for Your Modem ......................29  
PC Initialization Strings ......................................................30  
3.4.1  
3.4.2  
Changing Default Parameters......................................30  
Other Parameters ........................................................31  
3.5  
3.6  
Macintosh Initialization ......................................................31  
Configuring Software for Your Computer..........................32  
3.6.1  
Configuring Software for the Remote System ............32  
Terminal Emulation......................................................33  
File Transfer Protocols ..................................................33  
3.6.2  
3.6.3  
3
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
3.7  
When to Disable Data Compression ..................................33  
3.7.1 Disabling Error Correction ..........................................34  
Chapter 4 - Manual Dial and Automatic Answer  
4.1  
4.2  
4.3  
4.4  
4.5  
4.6  
4.7  
4.8  
4.9  
4.10  
4.11  
Introduction ........................................................................35  
Dialing/On-Line/Answering ..............................................35  
Auto. Leased Line Restoral Operation (336+ Only) ........37  
Manual Dial Backup Call Termination (336+ Only) ........37  
Dial Backup and Leased Line Restoral (336+ Only) ........37  
Dial-Up Operation (336+ Only)..........................................39  
Manual Call Origination......................................................39  
Automatic Answering ..........................................................40  
Manual Answering................................................................41  
Handshaking Details ............................................................41  
Call Termination ..................................................................42  
Chapter 5 - Command Mode  
5.1  
Introduction..........................................................................44  
5.1.1  
5.1.2  
AT Command Editing ..................................................44  
Functional Modes..........................................................45  
5.2  
5.3  
5.4  
Summary of AT Commands ................................................46  
Result Codes ........................................................................50  
Dialing Commands ..............................................................52  
5.4.1  
Dialing Action Commands ..........................................52  
Dial Modifier Commands ............................................54  
Phone Number Memory Commands ..........................58  
Configuration and Default Storage Commands ........60  
Command Response (Result Code) Commands........63  
Phone Line Conditioning Commands ........................66  
RS232C Interface Control Commands........................68  
Error Correction Commands ......................................70  
Flow Control Commands..............................................75  
5.4.2  
5.4.3  
5.4.4  
5.4.5  
5.4.6  
5.4.7  
5.4.8  
5.4.9  
5.4.10 Compression, Error Correction, Flow Control,  
Pass-Through and Pacing Commands ........................81  
5.4.11 Speed Conversion Commands ....................................82  
4
 
Table of Contents  
5.4.12 Immediate Action Commands ....................................85  
5.4.13 Line Probe Commands ................................................90  
Chapter 6 - S-Registers  
6.1  
6.2  
Introduction..........................................................................92  
Reading and Assigning S-Register Values ..........................102  
6.2.1  
6.2.2  
Examples of Assigning Values ......................................102  
Examples of Reading Values ........................................103  
6.3  
AT Command and S-Register Summary ............................103  
Chapter 7 - Callback Security and Remote  
Configuration  
7.1  
7.2  
7.3  
Introduction..........................................................................104  
Callback Feature Description ..............................................104  
Remote Configuration Description ....................................105  
7.3.1  
Initial Setup Procedures for Callback and Remote ..  
Configuration. ..............................................................105  
Remote Configuration Procedures..............................111  
7.3.2  
7.4  
7.5  
Remote Configuration and Callback Security AT ............  
Commands ..........................................................................112  
Remote Configuration/Callback Security S-Registers ......114  
Chapter 8 - Modem Testing  
8.1  
8.2  
8.3  
8.4  
8.5  
8.6  
8.7  
Introduction ........................................................................116  
Local Analog Loopback Test/V.54 Loop 3 ........................117  
Digital Loopback Test/V.54 Loop 2 (Local/Manual) ......118  
Digital Loopback Test/V.54 Loop 2 (Remote/Auto.) ......120  
Back-to-Back Test..................................................................121  
Synchronous Mode Testing ................................................123  
Local Analog Loopback Test (Synchronous Mode)..........123  
5
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
8.8  
8.9  
Digital Loopback Test (Local/Manual) (Sync Mode) ......124  
Digital Loopback Test (Remote/Auto.) (Sync Mode) ......125  
Chapter 9 - DIP-Switch Settings  
9.1  
9.2  
9.3  
9.4  
Introduction..........................................................................127  
DIP-Switch Option Settings ................................................128  
Speaker Volume Control ....................................................136  
Recording Option Configurations......................................137  
Appendix A - Troubleshooting  
A.1  
A.2  
Possible Causes and Solutions ............................................139  
Contacting Black Box ..........................................................147  
A.2.1 Recording Modem Information ..................................147  
A.2.2 Making the Call ............................................................148  
Shipping and Packaging ......................................................148  
Upgrading the Series II Modem’s Firmware......................149  
A.3  
A.4  
Other Appendixes  
Appendix B - Dial Pulse and Tone-Dial Frequencies ......................150  
Appendix C - Command Summary ..................................................151  
Appendix D - DIP-Switch Summary ..................................................164  
Appendix E - S-Register Summary ....................................................167  
Appendix F - Result Code Summary ................................................171  
Appendix G - V.25bis Operation........................................................174  
Appendix H - Series II Modem Cables..............................................187  
Appendix I - RS232C Interface Specifications ................................189  
Appendix J - Regulatory Information ..............................................195  
6
 
CHAPTER 1: Introduction and Description  
1. Introduction and Description  
1.1 Introduction  
Welcome to the world of data communications. You have acquired one  
of the finest intelligent desktop data/fax modems available today, a  
Series II Modem from Black Box. Your Series II Modem provides data  
communication at 33,600-14,400 bps (Enhanced V.34/V.32bis), as well  
as other prevalent datacomm standards. The Modem supports adaptive  
®
protocol enhancing used in typical Unix batch file transfers and  
®
®
support for IBM's AS/400 and System/3X environment. If your  
Series II Modem is a 336+ model, it also performs dial backup with  
automatic lease line restoration. This Owner’s Manual will help you  
install, configure, test and use your Modem.  
1.2 How To Use This Manual  
This manual is divided into nine chapters. There are also several  
appendices at the end of this manual, most of which repeat information  
contained in the chapters, but in a more condensed form. These appen-  
dices can be used as a quick reference. The information contained in  
each chapter and appendix is as follows:  
Chapter 1 - Introduction and Description  
This chapter begins with a short introduction, followed by a guide (which  
you are now reading) to the use of this manual. There is a discussion  
about what components you can expect in your Series II Modem  
package. We then provide a more detailed description of the modem,  
including the modem’s technical specifications. Chapter 1 includes  
sections covering power, LED indicators and a brief summary of PC  
board controls. (Chapter 9 covers switch settings more thoroughly.)  
7
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Chapter 2 - Installation and Connection  
Chapter 2 covers the procedure for connecting the Series II Modem to  
your computer and to the phone line. Details are given, supported by  
illustrations on the Modem's back panel connections as a guide to  
install your Modem to the point of operation.  
Chapter 3 - Software Configuration  
Chapter 3 documents communication software configuration  
recommended specifically for the Series II Modem. There is also some  
discussion of how to identify the limitations and capabilities of your  
computer before the software installation process is done. Other issues  
covered include setting up initialization strings, changing default  
parameters, configuring software for the remote system and file  
transfer protocols.  
Chapter 4 - Manual Dial and Automatic Answer  
This chapter covers some modem operations, but delays discussion on  
Command Mode operation until Chapter 5. Automatic Leased Line  
Restoration, Dial backup, Manual Dial Mode, and Answer Mode opera-  
tion are covered in detail, as well as the handshaking procedures  
employed between two modems in an auto-answer application.  
Chapter 5 - AT Command Mode Operation  
This may be the most important chapter of this manual. It begins with  
an introduction and discussion on Command Mode fundamentals. A  
flow chart is provided to illustrate Command Mode and On-Line Mode  
operation and the methods used in each mode. Next, there is a  
summary of the modem’s commands and responses. We then go into  
a detailed explanation of each Series II Modem command, providing  
examples where applicable.  
Chapter 6 - S-Registers  
Chapter 6 covers the Series II Modem's S-Registers, which enable the  
user to establish, read, and modify various modem options. All of the  
S-Registers are charted and explained, followed by instructions on  
accessing the S-Registers and reading or changing their values.  
8
 
CHAPTER 1: Introduction and Description  
Chapter 7 - Callback and Remote Configuration  
Chapter 7 documents instructions on how to operate the Series II  
Modem's Callback and Remote Configuration features; and the usage of  
LOGIN Passwords, Set-Up Passwords and Remote Escape Characters as  
network management tools.  
Chapter 8 - TestingYour Modem  
This Chapter covers the modem's built-in test features. These are:  
Power-on Self Test, Back-To-Back Test, Local Analog Loopback, Digital  
Loopback and Remote Digital Loopback Tests. We have included a  
description of each test and how to use each test procedure.  
Chapter 9 - DIP-Switches  
The Series II Modem printed-circuit board options are covered in this  
chapter. Sixteen DIP-Switch settings and the modem's speaker volume  
control are explained in detail, including all default settings.  
Appendix A - Troubleshooting  
Appendix B - Pulse Dial and Tone-Dial Frequencies  
Appendix C - AT Command Summary  
Appendix D - DIP Switch Summary  
Appendix E - S-Register Summary  
Appendix F - Result Code Summary  
Appendix G - V.25bis Operation  
Appendix H - Series II Modem Cables  
Appendix I - RS232 Interface Specifications  
Appendix J - Regulatory Information  
9
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
1.3 What is inYour Modem Package?  
Your Series II Modem is made up of many components. Make sure you  
have them all before trying to operate your modem. Your package  
should include:  
The Series II Modem itself  
AC Power Transformer  
(2) RJ-11 to RJ-11 telephone cords  
This Owner’s Manual  
336+ (MD1640A) only: (1) RJ-11 to spade lugs leased-line cable  
If any of these items are missing, please contact Black Box.  
1.4 Modem Features  
Your Series II Modem meets the proposed Enhanced V.34 ITU standard  
for data signalling rates as high as 33.6/31.2K bps in full duplex mode.  
Connections can be made on Public Switched Telephone Networks  
(PSTNs) and/or point-to-point 2-wire and 4-wire leased telephone type  
circuits. Enhanced V.34 is an extension of V.32/V.32bis/V34 standards,  
and supports and is compatible with those features, including EIA  
extended Automode; adaptive line probing; automatic symbol rate and  
carrier frequency during start-up; and retrain and rate renegotiation  
(in 2400 bps increments).  
Your modem is compatible with the AT command set and the ITU  
V.25 bis standard for sunchronous dialing. It also features ITU V.42  
error correction and V.42bis data compression, providing 100% error-  
free data transmission. V.42 error correction incorporates MNP (Classes  
3 and 4) and LAP-M. You may select V.42bis data compression for 4-1  
throughput, or MNP Class 5 for 2-1 throughput.)  
10  
 
CHAPTER 1: Introduction and Description  
Your Series II Modem offers interactive automatic dialing, as well  
as Command Mode option configuration. You may store up to ten  
command line/telephone numbers, of up to 60 characters each, in  
the modem’s nonvolatile memory. The modem pulse or tone dials,  
and recognizes dial tones and busy signals for reliable call-progress  
detection. The modem can detect AT&T calling card tones. It is  
FCC-Registered for connection to telephone networks without any Data  
Access Arrangements (DAA’s).  
Your modem also features Callback Security to protect networks from  
unauthorized use, and to manage phone line costs. By using the  
modem’s phone number and password directory, a host site can, upon  
receipt of a call, callback to a remote site at a predetermined number.  
Remote Configuration permits you to assist users at remote sites, saving  
you the time and trouble of site visits and preventing misinterpretation  
of configuration instructions.  
In addition, the major application for the 336+ (MD1640A) model of  
the Series II Modem is in 4-wire leased line networks with the addition  
of dial backup capability. With this capability, the dialup feature  
prevents downtime if the leased line fails. Since the Modem operates  
according to ITU V.34 modulation, it can operate full-duplex over two  
wires, so that the dial backup mode performs the same throughput as  
the leased line.  
1.5 Fax Features  
Your Series II Modem meets the ITU V.17 standard for sending and  
receiving faxes. When linked to a compatible fax machine or modem,  
it can transmit faxes at 14,4 K bps. It also meets the ITU’s Group 3  
Designation for sending and receiving faxes at 9600 bps; and Group 2  
Designation for sending and receiving faxes at 4800 bps. The Modem is  
also downward-compatible with modems to speeds as low as 300 bps, so  
it can send and receive faxes with any fax machine in the world.  
11  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
1.6 Technical Specifications  
Your Series II Modem data/fax modem meets the specifications listed  
below:  
Data Rates (modem)  
33,600, 31,200, 28,800, 26,400, 24,000,  
21,600, 19,200, 16,800, 14,400, 12,000, 9600,  
7200, 4800, 2400, 1200, 0-300 bps  
Data Rates (fax)  
Data Format  
14,400, 9600, 7200, 4800 bps  
Serial, binary, asynchronous at 0-300, 1200,  
2400, 4800, 7200, 9600, 12,000, 14,400,  
16,800, 19,200, 21,600, 24,000, 26,400,  
28,800, 31,200, 33,600 bps; synchronous at  
1200, 2400, 4800, 7200, 9600, 12,000,  
14,400, 16,800, 19,200, 21,600, 24,000,  
26,400, 28,800, 31,200, 33,600 bps  
Compatibility  
ITU V.42bis, V.42, Pending ITU Enhanced  
V.34 approval, ITU V.34, ITU V.32bis, V.32,  
V.22bis, V.22, V.25bis, Bell 212A and  
103/113, ITU V.17, Group 3 T.4, T.30 and  
EIA TR-29 Class 2  
Error Correction  
Data Compression  
Speed Conversion  
V.42 (LAP-M or MNP 3 & 4) error  
correction  
V.42bis, (4:1 throughput) or MNP 5  
(2:1 throughput) data compression  
Serial port data rates adjustable to 300,  
1200, 2400, 4800, 9600, 19,200, 38,400,  
57,600 and 115,200 bps  
Flow Control  
Options  
Xon/Xoff, Hardware RTS/CTS, ENQ/ACK  
Unix-to-Unix Copy Protocol (UUCP)  
"Spoofing"  
12  
 
CHAPTER 1: Introduction and Description  
Mode of Operation  
Intelligent Features  
Full duplex over both dial-up lines and  
2-wire or (336+ [MD1640A] only) 4-wire  
leased lines; automatic or manual dialing,  
automatic or manual answer; and (336+  
[MD1640A] only) automatic dial backup on  
separate lines in leased line operation  
Fully “AT command” compatible, micropro-  
cessor controlled remote configuration, EIA  
extended Automode, adaptive line probing,  
automatic symbol rate and carrier  
frequency during start-up, retrain and rate  
renegotiation, autodial, redial, repeat dial,  
dial linking, pulse or tone dial, dial tone  
detection, dial pauses, call status display,  
auto-parity and data rate selection,  
keyboard-controlled modem options,  
nonvolatile memory and on-screen displays  
for modem option parameters and up to  
ten telephone numbers/command lines of  
up to 60 digits each, help menus  
Command Buffer  
Modulation  
60 characters  
Trellis Coded Modulation (TCM) at 33,600,  
31,200, 28,800, 26,400, 24,000, 21,600,  
19,200, 16,800, 14,400, 12,000 and 9600  
bps, Quadrature Amplitude Modulation  
(QAM) at 9600 (non-trellis), 4800 and 2400  
bps, PSK at 1200 bps, FSK at 300 bps  
Fax Modulations  
V.21CH2 FSK at 300 bps  
V.27ter DPSK at 4800 and 2400 bps  
V.29 QAM at 9600 and 7200 bps  
V.17 TCM at 14400, 12000, 9600,  
and 7200 bps  
13  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Fax Carrier  
V.21CH2 (Half Duplex)  
Frequencies  
1650Hz Mark, 1850Hz Space for Transmit  
Originate  
1650Hz Mark, 1850Hz Space for Transmit  
Answer  
V.27ter 1800Hz Originate/Answer  
V.29 QAM 1700Hz Originate/Answer  
V.17 TCM 1800Hz Originate/Answer  
Lease Line Restoral  
Carrier Frequencies  
336+ (MD1640A) only: When in dial backup  
mode, modem attempts leased line restoral  
periodically (controlled by S-Register S18  
setting)  
1800 Hz V.32/V.32bis/V.34/Enhanced V.34:  
33.6K/31.2K/28.8K/26.4K/24K/21.6K/  
19.2K/16.8K/14.4K/12K/9.6K/7.2K/4.8K  
Carrier Frequencies  
2400 & 1200 bps  
(V.22bis/V.22 or  
Transmit Originate:  
Transmit Answer:  
Receive Originate:  
Receive Answer:  
1200 Hz  
2400 Hz  
2400 Hz  
1200 Hz  
Bell 212A Standard)  
Carrier Frequencies,  
1270 Hz Mark, 1070 Hz Space for  
300 bps (Bell Standard) Transmit Originate  
2225 Hz Mark, 2025 Hz Space for Receive  
Originate  
2225 Hz Mark, 2025 Hz Space for Transmit  
Answer  
1270 Hz Mark, 1070 Hz Space for Receive  
Answer  
Transmit Level  
-11dBm (dial-up), -9 or -15 dBm (leased-  
line); dBm level selectable with DIP-  
Switch #3 in leased line setting  
Frequency Stability  
0.01%  
14  
 
CHAPTER 1: Introduction and Description  
Receiver Sensitivity  
AGC Dynamic Range  
Interface  
-43 dBm under worst case conditions  
43 dB  
EIA RS-232C/ITU V.24  
Connectors  
Both models: (1) DB25 female for RS232C,  
(1) RJ-11 female for phone hadset, (1)  
Power inlet;  
336+ (MD1640A) model only: (1) RJ-11  
female for dialup line, (1) RJ-11 female  
for 2- or 4-wire leased line;  
336 (MD1641A) model only: (1) RJ-11 female  
for dialup line or 2-wire leased line  
Diagnostics  
Indicators  
Power-on Self Test, Local Analog Loop,  
Local Digital Loop, Remote Digital Loop,  
Back-to-Back Test.  
All front-mounted LEDs:  
Both models: Transmit Data, Receive Data,  
Carrier Detect, Speed Indicators, Off Hook,  
Terminal Ready, Error Correction, and Fax;  
336+ (MD1640A) model only: Error  
Controls  
Speaker  
Toggle switches for Power and for  
Voice/Data with Originate or Answer, DIP  
Switches for various modem options, and  
volume knob  
Speaker for call progress monitoring  
Operating Temperature 0˚ to 50˚C (32˚ to 120˚F)  
Power Requirements  
115-VAC, 60Hz, 0.3amp (2-prong outlet-  
mounted transformer)  
Dimensions  
Weight  
1.38"H x 6.2"W x 9"D (3.5 x 15.6 x 22.9 cm)  
1.6 pounds (0.7 kg) without transformer,  
2.6 pounds (1.2 kg) with transformer  
15  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
1.7 Power  
Power is supplied through an AC power transformer terminated with a  
standard two-prong plug. The transformer supplies low voltage AC to  
the modem, and plugs into any conventional 115 volt AC, 60 Hz, two-  
prong power outlet. The power transformer supplied with the modem  
is the only one that should be used. Use of any other transformer could  
cause damage to the modem. A Power On/Off switch is located on the  
back of the modem.  
1.8 Modem LED Indicators  
The Series II Modem has fourteen diagnostic LED indicators. They are:  
Answ  
Orig  
SD  
RD  
CD  
33.6  
24.0  
19.2  
14.4  
96  
24  
OH  
TR  
EC  
FX  
Voice/  
Data  
Send Rcv Carr 33.6K 24.0K 19.2K 14.4K 9600 2400 Off Hk Rdy V.42 Fax  
Answ  
Orig  
SD  
RD  
CD  
33.6  
24.0  
19.2  
14.4  
96  
24  
OH  
TR  
EC  
FX  
ERR  
Voice/  
Data  
Send Rcv Carr 33.6K 24.0K 19.2K 14.4K 9600 2400 Off Hk Rdy V.42 Fax Error  
Figure 1-1. LED Displays of the 336 (MD1641A, top)  
and 336+ (MD1640A, bottom)  
1) Transmit (Send) Data (SD). This LED blinks when data is being  
transmitted, on for a space, off for a mark. The state of this LED  
matches the TD circuit on Pin 2 of the RS-232C/V.24 interface.  
2) Receive Data (RD). This LED blinks when data is being received,  
on for a space, off for a mark. The state of this LED matches that of  
the RD circuit on Pin 3 of the RS-232C/V.24 interface.  
3) Carrier Detect (CD). This LED is lit when a valid carrier tone  
has been detected.  
16  
 
CHAPTER 1: Introduction and Description  
4) 28,800 bps (28.8). This LED behaves differently depending on your  
connection:  
• When the modem is connected at 33,600 bps, it blinks 5 times/sec.;  
• When the modem is connected at 31,200 bps, it blinks once/sec.;  
• When the modem is connected at 28,800 bps, it is solidly lit.  
Note: if the modem falls back to 26.4K bps while in V.34 mode,  
both the 28.8 and 24.0 LEDs light.  
5) 24,000 bps (24.0). This LED is lit when the modem is connected at  
24,000 bps. Note: if the modem falls back to 21.6K bps while in V.34  
mode, both the 24.0 and 19.2 LEDs light.  
6) 19,200 bps (19.2). This LED is lit when the modem is connected  
at 19,200 bps.  
7) 14,400 bps (14.4). This LED is lit when the modem is connected at  
14,400 bps. Note: if the modem falls back to 12,000 bps while in V.32bis  
mode, both the 14.4 and 96 LEDs light.  
8) 9600 bps (96). This LED is lit when the modem is connected at  
9600 bps.  
9) 2400 bps (24). This LED is lit when the modem is connected at  
2400 bps.  
10) Off Hook (OH). This LED is lit when the phone line is "off hook".  
This occurs when the modem is dialing, on-line, or answering a call.  
This LED also flashes when the modem is pulse dialing in Command  
mode.  
11) Terminal Ready (TR). When the TR LED is lit, the modem is  
permitted to answer an incoming call. When it goes off, a connected  
modem will disconnect. The state of the TR LED matches that of the  
DTR circuit on Pin 20 of the RS-232C/V.24 interface.  
12) Error Correction (EC). This LED is lit when the modem is set for  
V.42 error correction, and flashes on and off when data compression  
is activated.  
17  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
13) FAX (FX). This LED is lit when the modem is connected in FAX  
mode.  
14) 336+ (MD1640A) only: ERROR (ERR). When this LED is lit, either  
the leased line is down and the modem is in dial backup mode, or else  
the self-test has failed.  
1.9 Controls on PC Board  
The Series II Modem is designed on a single printed circuit (PC) board.  
This board contains one 16-position DIP-Switch (numbered 1-16). The  
DIP-Switches are accessible through a cut-out on the side of the  
modem. There is also a knob which is used to adjust the speaker  
volume. This knob is accessible through the modem's rear panel.  
The sixteen DIP-Switches control various modem options or set default  
values for Command Mode operation. There is a difference in how  
several of the switches operate depending on whether you are in syn-  
chronous or asynchronous mode. Refer to the switch label on the  
bottom of the Modem for an exact list of the switch functions in  
asynchronous and synchronous operation.  
Chapter 9 of this manual also provides detailed instructions on  
configuring all of the Modem's PC board options.  
18  
 
CHAPTER 2: Installation and Connection  
2. Installation and Connection  
2.1 Safety Warnings  
1. Never install telephone wiring during a lightning storm.  
2. Never install telephone jacks in wet locations unless the jack  
is specifically designed for wet locations.  
3. Never touch uninsulated telephone wires or terminals unless the  
telephone line has been disconnected at the network interface.  
4. Use caution when installing or modifying telephone lines.  
5. Avoid using a telephone (other than a cordless type) during an  
electrical storm. There may be a remote risk of electrical shock  
from lightning.  
6. Do not use the telephone to report a gas leak in the vicinity  
of the leak.  
19  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
2.2  
Installation  
The installation of the Series II Modem consists of making the physical  
connections necessary to render the modem functional with your  
computer. This includes making the proper serial, phone line, and  
power connections. Refer to Figure 2-1 below for the Series II Modem  
336 (MD1641A) or to Figure 2-2 on the next page for the Series II  
Modem 336+ (MD1640A). Following the installation instructions are  
some preliminary aspects of issuing AT commands and the Modem's  
"Originating/Answering" capabilities.The installation process involves:  
1. Verify the settings of DIP switches #5 (Originate vs. Answer mode)  
and #10 (Lease Line vs. Dial-Up operation). See Chapter 9.  
2. Attach the Series II Modem to a dialup phone line and/or a 2-wire  
leased line using the included RJ11 telephone cords. For the 336  
(MD1641A) model, run a cord from the LINE jack to the dialup  
20  
 
CHAPTER 2: Installation and Connection  
wall jack or the leased-line wall jack or terminal (refer to Figure 2-1  
below). For the 336+ (MD1640A) model, run a cord from the  
PSTN jack to the dialup wall jack if you’re connecting to a dialup  
line; run a cord from the LEASE jack to the 2- or 4-wire leased-line  
wall jack or terminal if you’re connecting to a leased line (refer to  
Figure 2-2 on the next page). 336+ (MD1640A) models only: For four-  
wire lines, the modem uses pins 1 and 6 to transmit and pins 2 and  
5 to receive.  
PHONE  
LINE  
INTERFACE  
ON  
OFF  
VOLUME  
POWER  
Figure 2-1. Series II Modem 336 (MD1641A) Connections  
PHONE  
PSTN  
LEASE  
INTERFACE  
ON  
OFF  
VOLUME  
POWER  
Figure 2-2. Series II Modem 336+ (MD1640A) Connections  
21  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
2. Attach your Modem to your PC or terminal with an RS-232  
(or V.24) cable.  
3. Connect telephone set to phone jack (if desired).  
4. Attach your Modem to the AC Power transformer and plug t  
he AC connector into a live AC outlet.  
5. Turn on power by flipping the "ON/OFF" switch at the left rear  
of the Modem to the "ON" position.  
6. Assuming you have already chosen Dial-Up mode (DIP Switch #10  
in the UP/OPEN position) or Leased Line mode (DIP-Switch #10  
in the DOWN/CLOSED position, assign your modem to either  
“originate” or “answer” mode. It doesn’t matter which mode you  
select — just give the modem you’re connecting to the opposite  
setting. For example, if you place DIP-Switch #5 UP, that modem  
will be the answering modem. Then you should place DIP-Switch  
#5 DOWN on the other modem so that it will be the originating  
modem. Again, it doesn’t matter which is which, as long as the local  
and remote modems have opposite settings.  
7. Verify transmit dBm levels. The transmit level for dial-up lines is -  
11dBm. The transmit level for leased lines is -9 dBm and may be  
set alternately to -15 dBm with DIP-Switch #3.  
8. Verify remote modem's current configuration settings with your  
Series II Modem in terms of data compression, error correction,  
transmission rate, etc. (per Chapter 5, Section 5.7.12, ATL5 and  
ATL7 Commands).  
9. Make sure modem and computer/terminal serial port baud rates  
are adjusted. (Note that several programs can check this for you.  
If you have MS-DOS 5.0 or higher, a program called MSD.EXE  
(Microsoft Diagnostics) is in your DOS directory. Typing MSD at  
the DOS prompt brings up a screen that provides a variety of  
information about your computer. Select COM ports and it lists  
information about your com port, e.g., UART Type, Address, and  
IRQ to name a few. Once you know your serial port's UART type,  
you can set your communications's software appropriately.)  
10. Verify self-test results (Section 2.2).  
11. Proceed to Chapter 3 of this manual, or to your data communica-  
tions software manual.  
22  
 
CHAPTER 2: Installation and Connection  
Note: Appendix A lists some basic and specific troubleshooting  
actions to take if your Modem is not operational.  
2.3 IsYour Series II Modem Ready for Use?  
As soon as you connected power to the modem, it performed a  
diagnostic self-test. The speed indicators flashed in sequence for  
approximately four seconds, then the 28.8 indicator is lit. The TR  
indicator should be lit as well. The SD, RD, CD, and OH indicators  
should remain off at this time. If not, check that the transformer is  
solidly connected and that your AC outlet is live.  
If you’re an experienced modem user, you may simply want to check  
your modem’s settings for data compression, error correction, and so  
on. You may find that you can get moving quite quickly if you just issue  
an ATL5, ATL6 and an ATL7 command. These commands lists how  
your modem is currently configured. If you come across a setting you’re  
unsure of, refer to Chapters 5 and 6 of this manual for AT command  
and S-Register explanations and defaults.  
If you’re a novice, please continue to the next sections of this chapter.  
23  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
2.4 OperatingYour Series II Modem  
You control your Series II Modem by issuing AT commands, setting  
S-Registers, and setting DIP-Switches. You can easily change the settings  
of your DIP-Switches, as they are located on the right side of your  
Modem’s chassis. Right now your Modem is set up for the most typical  
user application, that is, as a traditional modem set to make a dial-up  
call to a remote installation where the call is answered automatically;  
therefore, you shouldn’t need to change the DIP-Switches. (If however,  
you know that your application does not follow this profile, please refer  
to Chapter 9 of this manual for full details on DIP-Switch settings.)  
While you may operate your Series II Modem manually, it is more  
likely that you will use your data communications software to either:  
enter “terminal” mode, where you can “speak most directly” to  
the modem by issuing AT commands, or to  
launch a datacomm session through a set of modem configurations  
which you select and then associate with a target telephone  
number. Once you have created, saved, and named this set of  
information according to your connection needs and your  
datacomm software’s conventions, the software then simplifies  
your dialing because you needn’t re-configure your modem, nor  
run the risk of mistakenly keying-in incorrect information.  
Either way, you need to understand that an AT command is the method  
by which your modem is controlled, and must therefore prefix nearly all  
commands. AT stands for attention, and alerts the modem that a com-  
mand follows. You may enter these commands with either upper- or  
lowercase characters. Entering AT automatically sets the modem’s serial  
baud rate to match your computer’s and also sets the modem’s parity. It  
also clears the modem’s command buffer.  
Once you’re in terminal mode, enter AT followed by <CR> to check  
whether your modem is operational. If everything’s fine, your modem  
will respond OK. (If your Modem is a 336+ [MD1640A] model, refer to  
Chapter 4 for additional details on Dialing, Automatic Answering, Dial  
Back-Up and Automatic Leased Line Restoral.)  
24  
 
CHAPTER 2: Installation and Connection  
2.4.1 Simple Operations  
You can dial a number by using the ATD command and the phone  
number of the modem with which you wish to connect, e.g.,  
ATD6127853500. Your modem will dial the number, and hear a  
“scrambling” noise as the modem negotiates the kind of connection it  
can make, and once the modems have settled on a common  
connection, you will receive a connect message on your computer’s  
video display. As the modem dials and connects, you may notice  
changes across its front LED panel: the OH (Off Hook) LED lights to let  
you know the modem is operating as if you had picked up the handset  
to a phone. The CD (Carrier Detect) LED lights to let you know the  
modem has detected a device it can connect to. A speed LED lights to  
let you know at which speed the connection has been made.  
To hang up a call, enter +++ATH<CR>. Your modem will return on  
hook, just as if you had returned a phone’s handset to its cradle. Notice  
also that the OH, CD and speed LED’s are no longer lit. Your video now  
displays OK, signifying that your modem is ready for your next  
command.  
2.5 The Answer/Originate - Voice/Data Toggle Switch  
Located on the front of the modem is a Voice/Data "toggle" switch with  
Originate/Answer capabilities. This switch enables the modem to auto-  
matically dial a phone number stored in the N1 location of memory  
whenever this switch is toggled. (Note that you must first enter  
AT$VD1&W0<CR>. This command string enables Voice/Data dialing  
when the Voice/Data toggle switch is activated.)  
If you are "manually" dialing with an attached telephone device (and  
not with your keyboard), your Modem originates when this switch is  
toggled to the corresponding position (DOWN); and if you are  
"manually" answering (modem is not configured to automatically  
answer via S-Register S0 setup), the Modem answers when this switch  
is toggled to the corresponding position (UP).  
25  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
3. Software Configuration  
3.1 Introduction  
Since your communications software configuration is affected by the  
capabilities of your computer, this chapter begins with a discussion of  
the limitations of some serial ports and how to identify them. It then  
discusses communications configuration in general and recommends  
settings specifically for the Series II Modem.  
3.2 Serial Port Limitations  
When you configure your software, you need to consider how the  
hardware on both ends of the connection will affect the connection.  
Some serial ports, particularly those in older PC-compatible computers,  
may limit the performance of the Series II Modem. You should know if  
yours is one of them.  
The limiting factor is an integrated circuit called a Universal Asyn-  
chronous Receiver/Transmitter, or UART. All data from your modem  
flows through it. The UARTs typically used in PC-compatible computers  
are types 8250, 8250A, 16450, and 16550AFN. The 8250 is unreliable  
above 9,600 bps, and the 8250A and 16450 are unreliable above 19,200  
bps. If the modem sends data to the UARTs above those speeds, the  
UARTs may not be able to process the data fast enough to keep from  
losing some of it. The 16550AFN, however, can safely handle data to  
115,200 bps.  
When a modem communicates with V.42bis 4-to-1 compression en-  
abled, it sends up to four times as much uncompressed data to the serial  
port as it receives compressed over the telephone line. Therefore, a  
modem communicating at 14,400 bps may require a serial port that can  
reliably transfer data at four times 14,400 bps, or 57,600 bps; at 19,200  
bps it may require one that works reliably up to four times 19,200 bps,  
or 76,800 bps; and at 28,800 and 33,600 bps it may require one that  
works reliably up to a maximum of 115,200 bps. If your serial port  
cannot handle these speeds, we recommend that you replace your  
present serial card with one that has a 16550AFN UART or equivalent.  
26  
 
CHAPTER 3: Software Configuration  
®
Macintosh computers do not use UARTs. The Macintosh SE through  
®
IIfx models use a Zilog Z8530 chip called a Serial Communications  
Controller, or SCC, that has a maximum speed of 57,600 bps. This  
speed can be compromised by other serial communications, including  
®
printer transmissions and Appletalk , the networking software that  
allows Macintoshes to share files. When Appletalk is active it controls all  
serial communications on the Macintosh. Because it gives priority to  
network communications, it may lose modem data at higher  
transmission speeds. Therefore, when Appletalk is active you risk losing  
data on serial port communications over 2400 bps, though most users  
can work up to 9600 bps without problems. Other activities that could  
cause the serial driver to drop bits at high speeds include the floppy disk  
driver formatting a disk, the CPU paging in or out in virtual memory  
®
mode, and the Mac IIci or IIsi running the on-board video in 8-bit  
mode. Therefore, for maximum communications speed on the  
Macintosh, we recommend as few concurrent activities as possible. To  
use V.42bis compression at 19,200 bps or faster, we recommend that you  
install a high speed serial port card. Newer Macintosh computers, such  
as the Quadra and Centris models, support serial port speeds up to  
115,200 bps.  
3.2.1 How CanYou IdentifyYour UART Type?  
If you have MS-DOS 6.0 or later, you can find your UART type from  
a diagnostic program called MSD. To use it, type MSD at the DOS  
prompt. After the opening screen, select COM Ports.... The last line of  
the report tells you what type UART you have for each COM port. MSD  
does not distinguish between the 8250 and the 8250A. However, if you  
have an IBM AT or newer computer, you likely have an 8250A or 16450  
UART installed, both of which are reliable to 19,200 bps. If you would  
like more detailed information about your UART than MSD can  
provide, you can download shareware UART identification programs  
from the World Wide Web, from the IBM Communications Forum on  
®
CompuServe , or from a local BBS.  
27  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
3.2.2 The 16550 UART and Windows 3.1  
Windows 3.1 may cause a loss of data when communicating at high  
speed, even with a 16550 UART installed. Because Windows is multitask-  
ing—it switches between several programs running at the same time—  
it can make the serial port wait briefly while Windows performs other  
tasks. Meanwhile, incoming data can be lost. The older 8250A and  
16450 UARTs can store data in a one-byte first in-first out (FIFO) buffer  
(a memory area in the UART in which the first bit in is the first out),  
but once the buffer is full, the data is lost. The 16550 has a 16-byte FIFO  
buffer, which accounts for much of its high speed. However, in Windows  
3.1, the 16550’s FIFO buffer is disabled by default. To enable the buffer,  
use Notepad to open the SYSTEM.INI file in your Windows directory,  
and add the following line to the [386Enh] section:  
COMnFIFO=1  
where n is the number of the COM port the 16550 is installed on.  
For example, if the 16550 is installed on COM2, the line should be:  
COM2FIFO=1  
After you save SYSTEM.INI you must restart Windows for the change  
to take effect.  
However, there is another problem when the FIFO buffer is enabled:  
Windows cannot recognize the COM port because of a bug in the  
Windows 3.1 serial port driver, COMM.DRV. The only way around this  
problem is to replace the COMM.DRV file in the WINDOWS\SYSTEM  
directory with another driver. Several drivers are available commercially,  
on the World Wide Web, or on BBSes that will solve this problem.  
A freeware driver called CyberCom is available as CYBERC.ZIP on  
CompuServe in the IBM Communications Forum, Library 0. CyberCom  
will enable Windows communications at speeds up to 115,200 bps if you  
have a 16550 UART installed.  
28  
 
CHAPTER 3: Software Configuration  
3.3 ConfiguringYour Software  
Communications software must be configured to work with your mo-  
dem, your computer, and the remote system it is calling. Fortunately,  
most communications programs make the process easy by providing a  
default initialization string for your modem as well as defaults for most  
of the other required parameters.  
3.3.1 Configuring Software forYour Modem  
Because remote computers may have different connection re-  
quirements such as speed, number of bits, parity, log-on sequences, etc.,  
communications software is typically configured by sessions, each session  
having a unique configuration for a given connection (e.g., to the  
Internet, to a BBS, or to a commercial on-line service). Most communi-  
cations programs, however, have a separate modem configuration menu  
because modem configurations rarely change from session to session.  
The most important configuration is the modem initialization string.  
This is a sequence of commands the software uses to configure the  
modem when the communications software is loaded or when a session  
begins. Always begin the initialization string with the ATtention  
command AT, then follow it with the modem reset command, &F.  
Issuing a reset command before other commands ensures that you are  
starting with a known state.  
The rest of the commands in the initialization string depend on the  
capabilities of the modem and what you want it to do. Some older  
communications programs require you to create the initialization string  
by yourself. Most modern communications programs, however, provide  
you with a ready-made initialization string that is automatically selected  
when you choose your modem model from a list. It is a poor idea to use  
an initialization string intended for another modem, especially one  
from another manufacturer, because modem capabilities and command  
implementations vary from modem to modem. However, if your Series  
II Modem does not appear on a modem list, you may use any initializ-  
ation string labeled “MultiModemII” that might appear in the list.  
29  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
3.4 PC Initialization Strings  
We recommend the following initialization string for a Series II Modem  
connected to a PC-compatible computer when sharing a line with a  
telephone:  
AT &F X4 S0=0 ^M  
This string resets the Modem to the factory default settings, selects ex-  
tended result codes with NO DIAL TONE and BUSY, and turns off auto-  
answer. ^M must end every string sent to the modem from software.  
It is the ASCII code for the RETURN key on most keyboards, and the  
default code for the carriage return character in the Modem and most  
communications programs. The carriage return character is defined in  
the Modem in S-register S3; if you change it, you must also change the  
carriage return character code used in your communications software.  
If you send a command directly to the modem in terminal mode rather  
than indirectly through communications software, you must end the  
command string by pressing the RETURN key (<CR>) instead of adding  
^M to the string.  
The following initialization string is for a Modem on a telephone line  
that functions solely as a DATA LINE:  
AT &F X4 S0= 2 ^M  
3.4.1 Changing Default Parameters  
By default, the Series II Modem will answer after the first ring and try to  
communicate with a modem on the other end of the line. If you have  
one telephone line for voice, fax, and modem communications, the  
Modem may attempt to answer all incoming calls, voice as well as data.  
To change auto-answer to default off, open your communications  
program and type the following string in the terminal window:  
AT &F S0=0 &F9 &W0 <CR>  
30  
 
CHAPTER 3: Software Configuration  
This string selects the factory default parameters, then turns auto-  
answer off and stores that setting, along with all other current para-  
meters, in nonvolatile memory. The &F9 command causes the modem  
to load the values from nonvolatile memory the next time it receives  
the &F command. You will use the same initialization string as before:  
AT &F X4 ^M  
But now the Modem will load the values stored in nonvolatile memory  
when you turn on the modem and when you issue the ATZ or AT&F  
reset commands.  
Note: Because it clears the command buffer, you should not use ATZ  
in an initialization string.  
3.4.2 Other Parameters  
The default values for the other parameters in modem configuration  
menus rarely need changing. They typically include the dialing prefix  
(ATDT for touch-tone service and ATDP for rotary service), the dialing  
suffix (^M), the hang-up string (+++ATH0^M), and response messages  
(RING, NO CARRIER, BUSY, etc.). Communications software with a host  
mode might also include an auto-answer string (ATS0=1^M).  
3.5 Macintosh Initialization  
Macintosh computers cannot use RTS/CTS hardware flow control  
without a serial cable wired for hardware control. The Macintosh 128  
and 512 models cannot use RTS/CTS flow control at all. For those  
Macintoshes turn off the default RTS/CTS hardware flow control, turn  
on XON/XOFF flow control and pacing, and ignore DTR:  
AT &F X4 &E5 &E13 &D0 ^M  
For hardware flow control, use the following initialization string:  
AT &F X4 &E13 &D0 ^M  
Add S0=0 to both strings to disable auto-answer if the Series II Modem  
is on a voice line.  
31  
 
Chapter 3: Software Configuration  
You can store the initialization string in nonvolatile memory. With your  
communications software open and connected to the modem’s COM  
port, type the initialization string in the terminal window, substituting a  
carriage return for ^M. To store the string, enter  
AT &F9 &W0 <CR>  
Now you can initialize your modem with the following simple string:  
AT Z ^M  
3.6 Configuring Software forYour Computer  
You must configure your communications software to match your com-  
puter’s configuration. If the Series II Modem is connected to the COM2  
serial port, you must tell the software you are using COM2. Another  
important parameter is the serial port baud rate. This is the speed at  
which your modem communicates with your computer, not the speed at  
which your modem communicates with another modem. When V.42bis  
data compression is enabled, you must have a serial port baud rate four  
times the transmission speed of the modem to fully optimize  
compression. So if your UART is fast enough, you should set the serial  
port baud rate to a minimum of four times the top speed of your  
modem.  
If you have an 8250 UART, your most reliable serial port speed will be  
9600 bps; if you have an 8250A or a 16450 UART, try 19,200 bps; if you  
have a 16550 UART or equivalent, a serial port setting of 115,200 bps  
can be set reliably.  
3.6.1 Configuring Software for the Remote System  
You must meet the requirements of the remote system for successful  
communications. Though the Series II Modem can automatically match  
the speed of the other modem, you must specify parameters such as  
type of flow control, break length, number of data bits, number of stop  
bits, and parity. If you set these parameters incorrectly with the remote  
system, gibberish will appear on your screen.  
32  
 
User Guide for Series II Modems  
3.6.2 Terminal Emulation  
If you are accessing the remote computer as if from an on-site terminal,  
the keyboard codes used by your computer may not match the ones  
used by the remote computer. To be compatible with the remote com-  
puter, your software must be able to substitute the appropriate codes in  
what is known as terminal emulation. Most communications programs can  
emulate the most common mainframe terminals, including the DEC  
VT100, VT102, and VT52 terminals, and the basic TTY mode. If in  
doubt about which to choose for a Telnet session, a BBS connection,  
etc., try ANSI or VT100 first.  
3.6.3 File Transfer Protocols  
When you upload or download files with your Series II Modem through  
a browser, it will transparently use the appropriate protocol (usually  
http or ftp). When you are uploading or downloading through a  
terminal emulator, however, the host computer will ask which file  
transfer protocol you want to use. Most communications programs allow  
you to choose a default protocol. Your software’s documentation should  
list the ones it can use (not all communications programs support all  
protocols). Zmodem is the recommended protocol for most transfers.  
3.7 When to Disable Data Compression  
If your serial port cannot keep up because it has an older UART, you  
may lose data when using data compression. Also, the speed advantage  
hardware compression gives you is entirely dependent on how much  
the data being transmitted can be compressed. If the data is already in  
compressed form—a .ZIP or a .SIT file, for example—trying to com-  
press it more will actually slow the transmission slightly compared to  
transmitting the same file with compression disabled. This effect will be  
most noticeable if your modem negotiates MNP 5 compression with the  
other modem. V.42bis will not try to further compress a compressed file,  
but MNP 5 will.  
33  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
The command to disable compression is AT &E14 <CR>. If you have  
an older UART or if you use your modem mostly for downloading long,  
compressed files from BBSs, you may want to include the &E14  
command in your initialization string as follows:  
AT &F S0=0 X4 &E14 ^M  
As a general rule, you should try to transmit files in already-compressed  
form rather than relying on V.42bis hardware compression. Because  
software compression is more efficient than hardware compression, you  
will have a higher throughput with the former. Of course, this efficiency  
does not include the time spent compressing and decompressing .ZIP  
or .SIT files, but it will save on phone bills. And hardware compression  
will still be there for those occasions when it is inconvenient to  
compress a file with software. Note also that when you download files  
with compression disabled, you can use a slower serial port if you have  
an older UART.  
3.7.1 Disabling Error Correction  
By default, the Series II Modem is set to auto-reliable mode. In this  
mode the Modem determines during the handshake whether the other  
modem is using V.42 error correction. If it is, the Modem then switches  
itself to reliable mode and enables error correction. If it is not, the  
Modem remains in non-error correction mode.  
Normally, we recommend that you leave the Modem set to auto-reliable  
mode (&E1). However, you may encounter some circumstances in  
which the Modem will work better with error correction turned off. For  
example, it has been reported that on CompuServe error correction will  
slow file transfers at modem speeds of 9600 bps and under. If this is a  
problem for you, you can turn off error correction with the command  
AT &E0, or you can include the command in your initialization string as  
follows:  
AT &F S0=0 X4 &E0 ^M  
34  
 
CHAPTER 4: Manual Dial and Automatic Answer  
4. Manual Dial and Automatic Answer  
4.1 Introduction  
We’ll assume that yours is the very common application, where you are  
using a Series II Modem to dial up a remote computer. The Series II  
Modem has been factory preset for originating a call to a compatible  
33,600 bps modem (also set up for hardware flow control, V.42 error  
correction, V.42bis data compression and CTS/RTS operation). If the  
answering modem is not set up similarly, the Modem automatically  
adjusts to the appropriate protocol.  
4.2 Dialing/On-Line/Answering  
There are several basic steps for “originating” and “answering” in data  
communication mode:  
1.  
2.  
3.  
4.  
Load communication software  
Dial  
Establish On-Line connection  
Terminate Call  
A simple way to dial is from the keyboard of your computer or terminal.  
You enter a command on the keyboard to tell the Series II Modem to  
dial.  
If you use a sophisticated communications software package, the  
software tells you to enter phone numbers and other information. If  
this is the case, the software, and not you, gives the dialing commands  
to the modem. All of the commands, option registers and intelligent  
features of the Series II Modem are taken care of by the software.  
If you are giving commands directly to your modem (and not through  
your software), each command must begin with AT (ATtention  
Characters). AT characters may be entered in upper or lower case.  
35  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Entering AT automatically sets the modem’s speed to match the speed  
of the computer or terminal, and also sets the modem’s parity.  
The AT characters alert the modem that a command follows. The AT  
Command can also be used to clear the command buffer, by simply  
typing AT and hitting RETURN.  
The letter D in a command causes the modem to dial the numbers  
immediately following it (e.g., ATD7247465500). You have a choice  
of either pulse (ATDP) or tone (ATDT) dialing methods.  
The Modem responds with “CONNECT” on your video display after the  
number is dialed and a connection signal is detected (since the Modem  
defaults to Enhanced V.34/V.42/V.42bis, the actual response is  
"CONNECT LAPM COMPRESSED”), if the Series II Modem “connects”  
with a similar modem (see section 5.3 Result Code Summary). The  
modem is now in “On-Line” mode, and is ready to communicate with a  
host site.  
If no connection signal is detected within 45 seconds (this time period  
can be adjusted by S-Register S7), the Modem goes On Hook/hangs up  
and returns to Command mode. At this point, your video displays “NO  
CARRIER”.  
Enter +++ATH to Hang Up On-Line (bring modem on-hook), and  
terminate the modem's On-Line mode. At this point, your video  
displays “OK”.  
In addition to the call originating capabilities, the Modem can also  
automatically answer incoming calls. You need not be present. You can,  
however, control the situation by configuring the modem to either  
answer or not to answer, or to answer after a specified number of rings.  
This is done by setting the value of S-Register S0 (modem defaults to  
automatically answer an incoming call after one ring). Refer to  
Chapter 6 for S-Register details.  
36  
 
CHAPTER 4: Manual Dial and Automatic Answer  
4.3 Automatic Leased Line Restoral Operation  
(336+ Only)  
When the Series II Modem 336+ (MD1640A) is in Dial Backup mode, it  
periodically checks the leased line to see if it's operational and tries to  
restore the leased line if possible. S-Register S18 determines how often  
restoral attempts occur. The default for S18 is 30 minutes, and can be  
set in one minute increments from 10 to 255 minutes. Setting the  
restoral attempts under 10 minutes causes excessive breaks in the  
dial-up operation.  
Note: Both local and remote modems must have S-Register S18 set  
identically. Refer to Chapter 6 for more information on S-Register S18.  
4.4 Manual Dial Backup Call Termination (336+ Only)  
With your Series II Modem 336+ (MD1640A) in leased line mode (DIP-  
Switch #10 in the DOWN position) and with dial backup operation in  
process, there are two ways to manually terminate the dial backup call  
(other than automatic leased line restoral). In each case, you will try to  
establish the leased line connection because it is back in operating  
condition. The methods of dial backup call termination are:  
1) Manual Control. The "Voice/Data" switch can be used to change  
from a dial back line to leased line by toggling down once. When  
that is done, the Modem tries the leased line connection, and, if it  
is good, the modem disconnects the dial back call and establishes  
a leased line connection.  
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50  
milliseconds or more, a disconnect occurs. This is probably the  
most common method used by computer systems at the automatic  
answer end of the line to cause the answering modem to  
disconnect after toggling off procedures.  
4.5 Dial Backup and Leased Line Restoral (336+ Only)  
The dialing associated with the Series II Modem 336+ (MD1640A) when  
it's in "leased line with dial-back" mode, involves placing a call from the  
originating modem due to a leased line failure.  
37  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
After a preset period of time (determined by S-Register S18), the  
modem automatically tries to restore the leased line.  
The parameters used to determine if a leased line is down (so automatic  
dial back can occur), is based on the Series II Modem doing a “retrain”  
on the leased line due to an error condition in the transmission. An  
error condition is defined as a "hit" on the line (the Carrier gets  
interrupted).  
The retrain is a "handshake" procedure between the modems to  
establish the Carrier again. If the retrain fails, both modems (originate  
and answer modems) start their Dial-back timers. The time is  
determined by S-Register S19 settings. The S19 default setting is one  
minute. During that minute, the originate modem tries to establish the  
leased line link. If the leased line is established during that time, the  
timer is cleared and everything is back to normal. If the timer expires,  
the modems goes to dial-back mode.  
The purpose of the timer for the Answer modem is to determine when  
it accepts a dial-up call. When both timers have expired and the leased  
line has not been established, the dial-back procedure starts. The  
number dialed is the one stored in location N9 of the originate  
modem's phone number memory. In the preparation for proper  
dial-back operation, enter the proper number in the N9 location using  
the commands detailed in Chapter 5. Keep in mind that the number  
also can be dialed in V.25bis Command mode.  
38  
 
CHAPTER 4: Manual Dial and Automatic Answer  
4.6 Dial-Up Operation (336+ Only)  
When your Series II Modem 336+ (MD1640A) is used as a dial-up  
modem (DIP-Switch #10 in the UP position), it can both originate and  
answer calls. To originate calls, you use the automatic dialing capability  
of the Modem's Command mode.  
To do this, use the computer or terminal keyboard to enter a few  
command letters, followed by the phone number you wish to dial. If you  
have a computer with sophisticated communications software, you may  
end up talking back and forth with the software, and the software will  
take care of talking to the modem.  
It is still possible, however, to dial your data calls using a telephone set.  
There are few reasons why you would want to do this, but if you have a  
need to use the telephone set to dial, we explain how in the next  
section. We will delay our coverage of Command Mode autodialing,  
and all other Command Mode features, until Chapter 5.  
4.7 Manual Call Origination  
You can use the Series II Modem to both originate and answer calls.  
To originate calls in Asynchronous mode, you will most likely use the  
Modem's Command mode, and give the modem automatic dialing  
commands (we will delay our discussion of the Command mode until  
Chapter 5). When using your modem in Synchronous mode, the  
Command mode is disabled, so you must automatically dial your calls  
with a telephone set. To use manual dialing, you first connect an  
ordinary telephone set (either touch tone or rotary dial) to the  
modem's PHONE Jack, if you have not already done so. Next, set the  
speed selection, (DIP-Switches #13 and #14), to the speed at which you  
wish to communicate. These DIP-Switches are located on the side of the  
modem. (Refer to Chapter 9 for DIP-Switch settings.) Your computer or  
terminal may be set for up to 115,200 bps.  
When your telephone set is connected, you can use it to dial the  
modem you wish to call. Simply dial the number, and then listen to the  
dialed modem's answer tone. When you hear it, press the Voice/Data  
switch on the front of the modem down (to the Originate position). You  
don't have to hold it down. Just "toggle it" (press it once and let it go).  
39  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Once you press the switch, the tone you hear should change to another  
pitch, or change into a rough-sounding scrambled noise. You then  
replace the telephone handset in its cradle, and your data  
communications begins.  
Note that the Series II Modem may call manually via the keyboard  
command ATD, or by pressing the Voice/Data switch on the modem's  
front panel downward. To force the Modem to automatically answer  
calls, either type ATA, or press the Voice/Data switch on the modem's  
front panel upward.  
4.8 Automatic Answering  
The Series II Modem can be used as an automatic answering modem.  
No special modifications or settings are required other than making  
sure that the Auto-Answer select switch is set to Auto-answer enabled  
(DIP-Switch #5 UP).  
The Modem, when in its idle state, is set for Originate mode frequencies.  
An incoming ring signal automatically switches the modem into Answer  
mode.  
You can program the modem to answer a call after a certain number of  
rings using S-Register S0 (see Chapter 6). Refer to Section 4.10 for the  
handshaking procedures used by the Modem when in automatic answer  
mode.  
In many originate-only applications, you may wish to disable the  
automatic answer capability of the modem. If a telephone set is  
connected to the modem, you may wish to receive incoming calls in  
a voice mode for normal voice conversation. If auto-answer is not  
disabled, all incoming calls are answered by the modem, preventing  
voice communications. To disable automatic answer, place DIP-Switch  
#5 to the DOWN (Disable Auto Answer) position (refer to Chapter 9).  
Another way to disable automatic answer is to use S-Register S0 to  
configure the modem to answer on the nth ring, where n equals zero  
(0). Another alternative is to have the modem answer after five or six  
rings, which gives you time to answer it manually if you wish. (See  
Chapter 6 for S-Register information.)  
40  
 
CHAPTER 4: Manual Dial and Automatic Answer  
4.9 Manual Answering  
We have shown that the Series II Modem can automatically answer  
incoming calls. The Modem can also answer manually, under your  
control. The most typical application involves you and another person,  
who, after carrying on a voice conversation, want to convert to data  
communications between your modems without having to hang up  
and dial again.  
The problem here is that both modems are in originate mode. For two  
modems to communicate, one of them must be in originate mode and  
the other must be in answer mode. The solution here is to force either  
one of the two modems to Answer mode, and the other to Originate  
mode.  
The Modem can be forced into either Answer mode or Originate mode  
by using the Voice/Data switch on the front of the modem.  
In our example, let's say that you and your friend Bill have just had a  
voice conversation. Both of you have your telephones connected to your  
Series II Modems, and your modems are connected to computers or  
terminals. Set the speed switches to the proper speed on both modems.  
To switch to Data mode from Voice mode, you would switch the  
Voice/Data switch Down (to the Originate position), and Bill would  
switch his up to Answer. This switches your modem to the originate on-  
line mode, and Bill's to the Answer on-line mode. You would both then  
hang up your telephone handsets, and continue the conversation via  
your keyboards.  
4.10 Handshaking Details  
This section briefly explains what happens between two modems in a  
normal call. We are assuming that there are Series II Modems at both  
the originating and at the answering end of the telephone line. (If  
other brands of modems are used with our modems, they will still  
communicate, but each manufacturer tends to use slightly different  
delay timings and sequences, and many of the brands vary in their  
LED designations.)  
41  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
When a call is dialed from the originating modem, the called modem  
responds to the ringing by switching into Answer mode and by turning  
on its RI (Ring Indicator, RS-232C/V.24 Pin 22) signal as the rings are  
detected. (The Modem-MAC does not use DTR.)  
Note that in order for the called modem to be able to answer the call, it  
must have a high DTR (Data Terminal Ready) signal. This signal comes  
from the computer or terminal to which it is attached, on RS232C Pin 20.  
When the called modem answers the call, its OH (Off Hook) circuit  
comes on and the ringing stops. Two seconds after the call is answered,  
the called modem begins transmitting its answerback tone.  
The originating modem, which has been off hook and waiting for the  
answerback tone, turns on its transmitter when it hears the tone. Then  
after a one second delay, the orignating modem's CD (Carrier Detect)  
comes on.  
The called modem then responds to the originating modem by turning  
on its CD (Carrier Detect) signal, and the handshaking is completed.  
Note: With the modem in Reliable or Auto-Reliable mode, some  
additional handshaking takes place. This is explained in Section 5.4.8.  
4.11 Call Termination  
There are a number of ways to terminate a call, or simply stated, hang  
up. They are:  
1) Command Mode Control. To terminate a call by Command  
Mode, enter +++ATH then RETURN; or, send a BREAK signal  
followed by ATH and a RETURN.  
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50  
milliseconds or more, a disconnect occurs. This is probably the  
most common method used by computer systems at the automatic  
answer end of the line to cause the answering modem to  
disconnect after logging off procedures.  
3) Loss of Carrier. After a data connection is established, the  
modem disconnects if a loss of carrier occurs for 700 milliseconds  
(0.7 seconds) or more. Note that one cause of carrier loss would be  
if one of the modems disconnect normally.  
42  
 
CHAPTER 4: Manual Dial and Automatic Answer  
4) Abort Timer.  
Answer Mode: When OH (Off Hook) comes on, the called modem  
starts a forty-five-second timer and waits for a carrier signal from  
the originating modem. If carrier is not detected within this period,  
the modem disconnects (hangs up) and is ready for another call.  
Originate Mode: The abort timer functions the same as in answer  
mode, except that the timer begins after the modem has  
completed dialing, instead of when it first goes off hook. It is  
possible to change this forty-five second wait period to any other  
value (from 0 seconds up to 255 seconds), or to disable the timer  
completely by re-configuring S-Register S7 (see Chapter 6.)  
5) Inactivity Timer. Causes the modem to disconnect if no data is  
transmitted or received for a specified time. The timer is restored  
any time a character is passed through the serial port in either a  
send or receive state. This timer runs in both normal or reliable  
connections and is controlled by S-Register S30. The Inactivity  
Timer can be disabled by setting S30 to 0, which is the factory  
default setting.  
43  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
5. Command Mode  
5.1 Introduction  
AT commands are the means by which you, and your communications  
software, are able to communicate with and configure your modem.  
They enable you to establish, read, and modify parameters in addition  
to dialing. The following provides both a summary and a detailed  
explanation of the AT commands recognized by the Series II Modem.  
5.1.1 AT Command Editing  
The BACKSPACE key on your keyboard can be used to edit characters  
in the AT command line. An AT command is not executed until the  
RETURN key is pressed. The BACKSPACE key erases the previous  
character for reentering.  
The BACKSPACE key does not erase the AT characters once they are  
entered. If your keyboard has no BACKSPACE key, CTRL-H does the  
same thing. The character recognized by the modem as BACKSPACE  
may be changed to any other ASCII character with S-Register S5.  
If you wish to cancel an entire command that has been entered but not  
yet executed, enter CTRL-X. This also clears the command buffer. The  
effect is the same as backspacing to cancel the entire command, only  
quicker.  
Characters entered in a command are stored in the modem's Com-  
mand Buffer (memory) until executed by hitting RETURN. The  
Command Buffer's capacity is sixty characters. The Attention Characters  
AT do not count in the sixty allowed Command characters. Spaces,  
which may be used for increased display readability, may be used when  
entering a command, but are not stored in the Command Buffer and  
are not counted in the sixty allowed characters. Hyphens, parentheses,  
etc. are not allowed.  
If the sixty character limit is exceeded or if invalid characters are  
entered, the Command Buffer automatically erases, and an ERROR  
message appears. You would then re-enter your command within the  
sixty-character maximum, using only the allowed characters.  
44  
 
CHAPTER 5: Command Mode  
5.1.2 Functional Modes  
The Series II Modem can be in one of two functional states (see Figure  
5-1). These are "Command mode" and "On-line mode". (There is also an in-  
between state, "Wait-for-Carrier", where the modem is out of Command  
mode but not yet really On-Line.  
When the modem is initially powered up, it is in Command mode and  
is ready to accept commands from your keyboard or software. The  
Modem enters On-line mode after dialing, making a connection with  
another modem, and then detecting a valid carrier signal. If no carrier  
is detected within a certain time frame, the modem abandons the call  
and re-enters Command mode.  
Once on line, the modem exits On-line mode if one of two conditions is  
met. If the carrier is lost or intentionally dropped, the modem hangs up  
and re-enters Command mode. Also, if the Modem recognizes the  
Escape sequence for which it is configured (i.e., either the Escape  
characters in the serial data stream, the Remote Escape characters in  
the modulated data stream, or the Break signal), the Modem will exit  
On-line mode, retain the datacomm link, and enter Command mode.  
You can force the Series II Modem into On-line mode without dialing  
by sending the ATD or ATA command to the modem.  
45  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
+++AT  
COMMAND  
MODE  
Dial (D or A)  
HANG  
UP  
command, or  
incoming  
phone call  
WAIT FOR  
CARRIER  
no carrier  
detected  
carrier detected  
AT0  
command  
ON-LINE  
MODE  
carrier lost  
Figure 5-1. Functional Modes  
5.2 Summary of AT Commands  
A wide variety of autodial operations and modem options can be con-  
trolled when the Series II Modem is in Command Mode. Remember,  
nearly all commands begin with AT.  
These commands are organized into several functional groups. An al-  
phabetical summary of commands is provided in Appendix D.  
HOW TO  
COMMANDS  
DIAL  
D Dial  
A: or : Continuous Redial  
$D  
$VD  
N
DTR Dialing  
Voice/Data Dialing  
Dial a Stored Number  
MODIFY DIALING  
PROCEDURES  
P/T  
&P  
,
Y
W
Pulse/Tone Dialing  
Set Pulse Dial Ratios  
Automatic Pauses in dialing  
Long Space Disconnect  
Wait for New Dial Tone  
46  
 
CHAPTER 5: Command Mode  
;
Return to Command Mode After Dial  
Command  
R
!
Reverse Mode of Operation  
Flash On Hook  
$
@
AT&T "Calling Card" Tones  
Quiet Answer  
MEMORIZE PHONE  
NUMBERS  
D...N  
NN  
L
Store Phone Numbers  
Number Linking  
List Numbers Stored in Memory  
STORE MODEM  
CONFIGURATIONS &W  
AND DEFAULTS  
&F  
Load Factory Defaults  
Store Configuration & S-Register  
Parameters  
Z
Reset Modem  
$SP  
#V  
UNIX/"Spoofing”  
336 (MD1641A) only: Enable/Disable  
V.32terbo  
&M  
&X  
Synchronous/Asynchronous Mode  
Select  
Synchronous Transmit Clock Select  
CONFIGURE  
COMMAND  
RESPONSES  
Q
Result Codes Enable/Disable  
Response  
&Q  
E
V
Result Code Selection  
Echo Command Characters  
Result Code Terse/Verbose  
Result Code...Basic/Extended/Call  
Progress  
X
CONDITION  
PHONE LINE  
AND MODEM  
HARDWARE  
&G  
M
&T  
#T  
Guard Tones  
Enable/Disable Monitor Speaker  
Remote Digital Loop Signal  
Enable/Disable Trellis Coded  
Modulation  
#F  
$FC  
Fallback When On-Line  
336+ (MD1640A) only: Enable/Disable  
Lowspeed Fast Connect  
Cleardown at Disconnect  
Auto-Speed Detect  
&CD  
#A  
47  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
CONTROL RS232C &C  
Carrier Detect Control  
INTERFACE  
&D  
&R  
&S  
&RF  
&SF  
Data Terminal Ready Control  
Clear To Send Control  
Data Set Ready Control  
CTS/RTS Control  
DSR/CD Control  
CONFIGURE  
ERROR  
CORRECTION  
&E0  
&E1  
&E2  
#L0  
Normal Mode  
Auto-Reliable Mode  
Reliable Mode  
Negotiate V.42 Mode During  
Handshake  
#L1  
#L2  
#L3  
$A  
MNP On/LAPM Off  
LAPM On/MNP Off  
Direct LAPM/Phase Out Handshake  
Auto-Reliable Buffering  
Enable/Disable Auto-Reliable  
Fallback Character  
$F  
$R  
$E  
Retransmit Count  
Error Correction at 300 bps  
CONFIGURE  
FLOW CONTROL  
&E3  
&E4  
&E5  
&E6  
Flow Control Disabled  
Hardware Flow Control  
Xon/Xoff Modem-Initiated  
Xon/Xoff Modem Responds/No Pass-  
Through  
&E7  
Xon/Xoff Modem Responds/Pass-  
Through Allowed  
#X  
Send Single/Multiple Xoff Characters  
Enq/Ack Off  
Enq/Ack On  
Normal Mode Modem Flow Control  
Off  
&E8  
&E9  
&E10  
&E11  
Normal Mode Modem Flow Control  
On  
&E12  
&E13  
&BS  
Computer-Initiated/Off  
Computer-Initiated/On  
Maximum Block Size  
48  
 
CHAPTER 5: Command Mode  
$EB  
336 (MD1641A) only: 10/11-Bit  
Asynchronous Format  
#P  
Parity Selection  
CONFIGURE DATA &E14  
Data Compression Disabled  
Data Compression Enabled  
COMPRESSION  
&E15  
CONFIGURE SPEED $BA0 Speed Conversion On  
CONVERSION  
$BA1 Speed Conversion Off  
$MB  
Set modem speed (e.g., $MB33600)  
$SB  
Set serial port speed  
(e.g., $SB115200)  
EXECUTE  
IMMEDIATE  
ACTION  
$H  
I
I 9  
L5  
L6  
L7  
Help  
Product Code Inquiry  
Windows 95 Autodetect Inquiry  
List Current Operating Parameters  
List S-Register Values  
List additional Configuration  
Parameters  
COMMANDS  
L8  
H
List On-Line Diagnostics  
Off Hook  
+++AT<CR>  
Escape Sequence: Entering  
Command Mode while On-Line  
Escape Sequence Options...Entering  
Command Mode while On-Line  
Force Answer Mode  
Exit Command Mode/Go Back On-  
Line  
%E  
A
O
EXECUTE  
LINE  
%DF  
Format Line Probe Display (Graph or  
Table Format)  
PROBE  
COMMANDS  
%DP  
L9  
Enable/Disable Reading Line Probe  
Display of Signal Strength  
Information  
L10  
L11  
&RP  
Display Signal to Noise Ratio (SNR)  
Display of Noise Information  
Initiates Retrain to Read Line Probe  
Parameters  
49  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
READ AND  
ASSIGN  
Sr?  
Sr=  
Read Current S-Register Value  
Assign S-Register Value  
S-REGISTER  
VALUES  
REMOTE  
#CBN Passwords for Callback Phone #s  
CONFIGURATION  
& CALLBACK  
SECURITY  
#DB  
#I  
#RCBNxx  
Callback Security Enable/Disable  
Change LOGIN Password  
Erase Password Linked with  
Memory Location xx  
#S  
Change SETUP Password  
TEST MODEM  
U
&T  
Self-Test Modem (Chapter 8)  
Enable/Disable Digital Loopback  
Signal  
5.3 Result Codes  
The Series II Modem Command mode provides you with several re-  
sponses, or “Result Codes”, that can aid you in Command mode  
operation. These Result Codes are displayed on your video monitor.  
You can choose result codes that closely match those of the standard AT  
command set, or choose enhanced function result codes that have been  
used in Series II Modems (“Series II" responses). The &Q command  
selects which result codes will be used.  
You can choose to have these Result Codes displayed in either “verbose”  
(full words) or “terse” (digits) format. This is controlled by the ATV0  
(terse) or ATV1 (verbose) commands. The Series II Modem defaults to  
verbose format.  
AT&Q0 selects Series II responses with Reliable/LAPM/Compression  
modifiers. The terse response code for CONNECT 2400 is 9. AT&Q1  
selects Standard AT command set responses. The terse result code for  
CONNECT 2400 is 10.  
50  
 
CHAPTER 5: Command Mode  
The following tables define the result codes generated by the &Q  
command (refer to Appendix G for Result Code Summary).  
Table 5-1 &Q0 "Series II" Result Codes  
TERSE  
0
1
2
3
4
5*  
6
7
VERBOSE  
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
NO DIALTONE  
BUSY  
TERSE  
11*  
12*  
13*  
19*  
21*  
24*  
26*  
28*  
VERBOSE  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
CONNECT 21600  
CONNECT 24000  
CONNECT 26400  
CONNECT 28800  
CONNECT 31200  
CONNECT 33600  
8
9*  
NO ANSWER  
CONNECT 2400  
31*  
33*  
* With MNP error correction on, RELIABLE (or R) is added to these result  
codes. With LAP-M error correction on, LAP-M (or L) is added to these result  
codes. With data compression on, COMPRESSED (or C) is added. (Note these  
"Extended" Result Codes are displayed when your modem is set up to do so with  
an X1, X2, X3, or X4 command.)  
Table 5-2 &Q1 “Standard AT” Result Codes  
TERSE  
VERBOSE  
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
NO DIAL TONE  
BUSY  
TERSE  
11  
12  
13  
19  
21  
24  
26  
28  
VERBOSE  
0
1
2
3
4
5
6
7
8
10  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
CONNECT 21600  
CONNECT 24000  
CONNECT 26400  
CONNECT 28800  
CONNECT 31200  
CONNECT 33600  
NO ANSWER  
CONNECT 2400  
31  
33  
*Reliable/Compression modifiers are not displayed with Standard AT Result  
Codes.  
51  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
5.4 Dialing Commands  
5.4.1 Dialing Action Commands  
Dial Command D  
The letter D in a command causes the Series II Modem to dial the  
telephone number immediately following it. For example, if you enter  
ATD5551212 and hit RETURN, the Modem dials the number 555-1212.  
The D command is also used in conjunction with a telephone set for  
manual dialing. You dial the number on your telephone set, and after  
hearing the answer tone on your handset, you type ATD on your  
keyboard and hit RETURN. Then hang up the headset. Unless you have  
a specific need to dial in this manner, we recommend you use the first  
method, where the telephone number is entered on your keyboard.  
The Series II Modem gives you several choices of dialing methods. You  
can use tone or pulse dialing, by inserting a letter T or a P in the  
command string. (See the section on Dial Modifiers.)  
You can also configure the modem to either wait for and detect dial  
tones and busy signals (which we call “Wait-for-Dial-Tone” dialing or  
“Smart” dialing), or work with timed pauses without dial tone and  
busy signal detection (which we call “Blind” dialing; see Section on “  
X” Command.)  
Note: There is another method of dialing, called “DTR Dialing”, where  
by manipulating the DTR signal on pin 20 of the RS-232C/V.24  
interface, a number stored in the modem's memory is automatically  
dialed. See the section on the DTR Dialing ($D) command for details.  
Continuous Redial A: or :  
If you select the Wait-For-Dial-Tone method of dialing (see X3 or X4  
command), you can command the Series II Modem to continuously  
redial a busy number until your call is answered. This is done with the  
A: command.  
52  
 
CHAPTER 5: Command Mode  
This command would be used only if you had already reached a busy  
number after executing a normal dial command. You simply enter A:  
(you need not enter AT, nor do you need to hit RETURN), and the  
modem will redial the number for you. If you again reach a busy signal,  
it re-dials again and again until it no longer detects a busy signal. You  
can stop the Series II Modem from re-dialing by pressing any key.  
Another method used to cause the modem to redial a phone number  
continuously is to enter a colon : at the end of the phone number. The  
result is the same as if you had entered A: after personally observing  
that the number was busy on the first dialing attempt. Using the colon  
in the dialing string is a step saver.  
Dialing a Stored Number N  
A telephone number that you have stored in the Series II Modem’s  
number memory may be automatically dialed by entering ATNn where  
n = 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. For example, a number stored at N3  
would be dialed by entering ATN3 and RETURN. Do not include the  
letter D in this command, or the stored number will be erased (also see  
Section 5.4.3., on Phone Number Memory Commands).  
DTR Dialing $D  
An alternate method of causing the Series II Modem to automatically  
dial is DTR Dialing. Data Terminal Ready (DTR) is a signal that comes  
into the modem from the terminal or computer to which it is  
connected, on pin 20 of the RS232C interface. In DTR dialing, the  
modem automatically dials a stored number as soon as it receives a high  
DTR Signal. The DTR dialing method is popular in synchronous appli-  
cations.  
To activate DTR Dialing, enter AT$D1 and hit RETURN. The modem  
dials the phone number stored in the N0 location of memory when it  
receives a high DTR signal. DTR must remain high for the duration of  
the call, until disconnect. To deactivate DTR dialing, enter AT$D0 and  
hit RETURN.  
Note that when you use DTR Dialing in a synchronous application, you  
need to make sure DIP-Switch #8 is in the UP position to disable V.25bis  
Command mode.  
53  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Voice/Data Dialing $VD  
Another alternate method of causing the Series II Modem to  
automatically dial is Voice/Data Dialing. With Voice/Data Dialing, the  
modem automatically dials the phone number stored in the N1 position  
of memory whenever the Voice/Data switch is toggled. You must first  
enter AT$VD1&W0<CR>. This command string enables Voice/Data  
dialing when the Voice/Data toggle switch is activated. To disable  
Voice/Data Dialing (default), enter the command AT$VD0 W0<CR>.  
5.4.2 Dial Modifier Commands  
There are several command characters that can be included within a  
dialing command (following the letter D), called “Dial Modifiers”. They  
have various functions, including the selection of Pulse or Tone Dialing,  
pauses in the dial sequence, automatic re-dials if a number is busy, and  
reverting to the Command mode or switching to the Answer mode after  
dialing.  
Pulse or Tone Dial P or T  
The Series II Modem dials numbers using either pulse or tone dialing,  
or a combination of both methods. Pulse dialing is a method used by  
rotary-dial telephones, which involves the timed opening and closing of  
line relay.  
Tone dialing is the method used by push-button (touch tone) telephones,  
and is sometimes referred to as DTMF, or Dual-Tone Multi-Frequency  
dialing.  
The method used is selected by including a P for Pulse or a T for Tone  
in the dialing command, right before the digits you wish to have dialed  
in that manner.  
For example, you would pulse-dial the number 555-1212 by entering  
ATDP5551212 and hitting RETURN. You could tone-dial the same  
number by entering ATDT5551212 and hitting RETURN. If neither  
Pulse nor Tone dialing is specified in the dial command, the Series II  
Modem uses whatever method used last. If the modem has been reset or  
just powered up, it uses Pulse dialing, even if the letter P is not included  
in your dial command.  
54  
 
CHAPTER 5: Command Mode  
Nearly all telephone systems in the U.S. are now compatible with tone  
dialing. Since that is the faster method, you will probably choose the  
tone method for your dialing.  
An example of combining pulse and tone dialing could involve a PBX  
system where 9 had to be pulse-dialed first, then the rest of the number  
tone-dialed after pausing for a second dial tone. The number would be  
dialed by entering ATDP9, T5551212 and RETURN. (The comma  
causes a pause, which we’ll explain soon.)  
Set Pulse Dial Ratios &P  
This command sets the time ratios between the open and closed  
portions of the dialing pulse frequencies. To select a dialing pulse ratio  
of 60 mSec/40 mSec, enter AT&P0. To select a ratio of 67 mSec/  
33 mSec, enter AT&P1. The factory default is &P0.  
Automatic Pauses in Dialing ,  
You can cause the Series II Modem to pause during the dialing  
sequence by entering a comma character where the pause is desired.  
This pause lasts two seconds. If a longer pause is desired, more than one  
comma may be entered consecutively, with each comma causing a two  
second pause. You also have the option of changing the length of the  
pause caused by the comma, from two seconds to any other value from  
0 up to 255 seconds. This is done by setting S-Register S8 (refer to  
Chapter 6). Each comma in a dialing command counts as one of the  
sixty allowed characters.  
Long Space DisconnectY  
When two modems are connected in Normal mode (that is, without  
error correction) there is no "polite" means of requesting a disconnect.  
A link disconnect request packet is sent under reliable connections. As a  
result some "garbage" may be received when a hang-up command is  
issued. The Y1 command enables the modem to use the break signal  
which accomplishes the hang-up as an instruction to shut off its receiver  
and disconnect (both modems must have Y1 enabled for this feature to  
be effective). Y0 (factory default) disables this function.  
55  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Wait for New Dial-Tone W  
A W inserted in the dialing command causes the Series II Modem to  
wait for another dial tone, and not resume dialing until another dial  
tone is detected.  
It is not necessary to enter a W at the beginning of the dialing  
command to wait for a modem dial tone, because the modem  
will do that first (pause automatically).  
In order for this command to work, you must select Wait-For-Dial-Tone  
dialing with the X2 or X4 command, so that your modem will be able to  
detect the dial tone.  
Return to Command Mode after Dial Command Execution ;  
A semicolon (;), entered as the last character of a dialing command  
causes the Series II Modem to return to the Command mode  
immediately after executing the command, instead of waiting for a  
carrier signal and going on line.  
For example, entering ATDT5551212; would tone-dial the number, and  
do nothing afterwards except go back into Command mode. This can  
be useful in dialing applications where modem data transfer is not  
desired, such as voice communications, or in applications involving  
the use of touch tones as a data entry method, such as bank-by-phone.  
Reverse the Mode of Operation R  
In certain operations you may need to reverse the mode of operation  
for your modem from originate to answer or answer to originate so that  
it would answer the phone and go into answer mode. This command  
turns off the reversing function with the R0 command and turns it on  
with the R1 command with the modem in either command mode. If  
you want to reverse from the originate mode, use R (with no number)  
in the dialing string.  
56  
 
CHAPTER 5: Command Mode  
Flash On Hook !  
Some switchboard systems react to a momentary On Hook. An  
exclamation mark inserted in the command causes the modem to  
“flash” on hook for a half of a second, as if you had held the switch hook  
button on a telephone down for a half second.  
For example, to flash On Hook after dialing the number 555-1234  
in order to transfer to Extension #5678, you might enter  
ATDT5551234,,!5678. The commas cause a 4 second pause (just to  
be safe).  
"Calling Card" Detect Tones $  
The Series II Modem has the capability to detect AT&T "calling card"  
tones for the purpose of utilizing the user's calling card number to  
originate an on-line connection. An $ symbol placed in the dialing  
string causes the modem to pause and wait for an AT&T "calling card" or  
a 1600 Hz tone (prevalent in the United Kingdom). When the tone is  
detected, the rest of the dialing string is processed. If no tones are  
detected within the time period set by S-Register S7 (default 45  
seconds), the modem will abort by indicating a NO CARRIER message.  
Hitting any key also aborts the $ command.  
The following is an example of this command:  
ATDT101099907247465500$0123 4567 8910 1112  
Quiet Answer @  
The @ command causes the Series II Modem to wait before processing  
the next symbol in the dialing string. The wait is for one or more  
ringbacks followed by 5 seconds of silence. If the time specified by  
S-Register S7 passes before the rings and silence, a NO ANSWER (R)  
result code is processed. The @ command is used for accessing a system  
that does not provide a dial tone.  
For example, ATDT5551212@7465500 causes the Series II Modem to  
dial the first number (555-1212) and wait for the time specified in S7  
57  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
for at least one ringback and 5 seconds of silence. If a busy signal is  
detected, the Series II Modem hangs up and generates a BUSY result  
code. If it does not detect 5 seconds of silence, a NO ANSWER result  
code is generated after hanging up. If 5 seconds of silence is detected,  
the second number (746-5500) is then dialed.  
5.4.3 Phone Number Memory Commands  
Storing Phone Numbers D...N  
A telephone number and command line of up to sixty characters may  
be stored in the Series II Modem’s number memory. As many as ten of  
these numbers may be stored. Each number will be given a name, using  
the codes N0, N1, N2 up to N9.  
A phone number is stored by entering ATD, then the number as it  
would be dialed, along with any P, T, R, ; or comma characters, and  
then entering N followed by the number’s “name,” which would be  
any number from 0 through 9, and then hitting RETURN.  
For example, the tone-dialed number 1-612-631-3550 would be stored  
as number N3 by entering ATDT17247465500N3 and RETURN. The  
number is not dialed with this store command. After storing a number,  
check to see that it has been stored correctly by typing ATL and hitting  
RETURN.  
When phone numbers are stored, the entire command line is also  
stored so that you can effectively create a macro for each number. For  
example, if you know a particular number needs to have extended  
result codes, detect busy or dial tone, error correction, Xon/Xoff flow  
control, pacing, and data compression enabled, the command line  
would be:  
ATX4&E1&E5&E13&E15DT17247465500N3  
This would store the entire command at location N3.  
Number Linking NN  
You may command the Series II Modem to dial another number  
automatically if the first number dialed is busy. This would be useful in  
a situation where a computer can be accessed through more than one  
phone number. This is called “linking”.  
58  
 
CHAPTER 5: Command Mode  
To link the number in N1 to the number N2, simply enter ATN1N2 and  
hit RETURN. Several numbers can be linked in the same command.  
For example, you could link N1 to N2 to N3 to N4 by entering  
ATN1N2N3N4 and RETURN or you could link N1 to N2 and back to  
N1 and then back to N2 by entering ATN1N2N1N2 and RETURN.  
The only limit on the number of numbers that can be linked is the 60  
characters allowed in a command line. Number linking can not be used  
with blind dialing, since busy signals would not be detected. You would  
have to select the Wait-for-Dial tone dialing method using the  
X Command in order to use the Number Linking feature.  
Listing Numbers Stored in Memory L  
Telephone numbers that you have stored in the Series II Modem’s  
memory may be listed and displayed with the L command. It will display  
all ten stored N numbers in a format like that shown below. All digits  
and command letters will be shown. The phone number’s single-digit  
designation (0 through 9) is shown first, followed by the complete  
dialing command and telephone number as originally entered.  
Simply enter ATL and hit RETURN to display these numbers on your  
video screen or printer. An example of an L command listing is shown  
below:  
0
1
2
3
4
5
6
7
8
9
DT14922345678  
DT17245551212;  
DP9,T14929876543  
DT3738315,12101,17247465500  
DT7465500R  
DP9,4258513  
DTX4&E1&E5&E13&E15DT17247465500  
DT12138880123  
59  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
5.4.4 Configuration and Default Storage  
Commands  
Store Configuration & S-Register Parameters  
in Non-Volatile Memory &W  
The Series II Modem can store configuration parameters and S-Register  
values in its nonvolatile read/write Random Access Memory (RAM)  
memory. The &W command does this, which prevents any re-  
configuration from being lost on a power-down or Reset (ATZ)  
condition.  
(access/phone number)  
(credit-card number)  
&W0 (or AT&W) causes the Modem to store your customized AT  
command settings and S-Register values in its nonvolatile RAM. &W0  
also sets the modem so that it reads your customized settings stored in  
nonvolatile RAM when powered down or reset. (The &W0 command  
only changes the settings stored in nonvolatile RAM that you specifically  
intend to alter. All other default parameters are applicable.)  
&W1 causes the Modem not to store your customized settings to  
nonvolatile RAM so that, after powering down or resetting the modem,  
it reads the factory default settings stored in ROM.  
Loading Factory Defaults &F  
The &F command provides a choice between customized configuration  
settings in RAM and the factory default configuration settings in ROM.  
The &F8 and &F9 commands define the function of the &F command.  
The Series II Modem is shipped from the factory with a pre-configured  
set of command and S-Register default settings. This set of factory de-  
faults can be recalled by issuing the &F command.  
In addition to being able to recall the factory-installed defaults, the &F  
command can also recall those defaults stored under &W0.  
This is done using the &F9 command. If you have stored parameters  
with the &W0 command and wish these settings to always be used as  
your defaults, you would enter &F9&W0.  
To return the &F command to read factory installed defaults, enter  
&F8&W0. &F8 is the factory default.  
60  
 
CHAPTER 5: Command Mode  
Many datacomm program issue the &F command automatically—the  
&F9 command allows the user to select their own factory defaults. Note  
that the &F8/&F9 commands should be used with &W0.  
Following is a summary of how the &F and Z reset commands interact  
with the &W command; note how the &F reset command operates  
differently from the Z reset command:  
Previous Command AT&F  
Power-On and ATZ  
AT&W1 (default)  
AT&W0  
AT&F8&W0  
AT&F9&W0  
ROM  
ROM  
ROM  
NVRAM  
ROM  
NVRAM  
NVRAM  
NVRAM  
Modem Reset Z  
The Z command can be used to reset the entire Command Mode  
buffer and the result is the same as if you had disconnected, and  
then reconnected power to the modem. When an ATZ command is  
executed, the state of the &W command determines where the default  
values originate. &W0 defaults come from RAM and &W1 defaults  
come from ROM.  
Unix UUCP Spoofing $SP  
The Series II Modem can be configured in a Unix environment that  
employs ACK flow control as a means of monitoring data integrity. The  
Modem can do “UUCP spoofing”, where the modem is able to generate  
ACKs at the DTE interface. Data is transmitted more time efficiently  
because the delay of waiting for data to be received, then for an ACK  
to be returned at the remote end, is eliminated. The $SP1 command  
enables UUCP spoofing and the default command $SP0 disables  
UUCP spoofing.  
V.32terbo Enable/Disable #V (336 Only)  
Other types of V.32/V.32bis modems have problems handshaking when  
the Series II Modem 336 (MD1641A) includes V.32terbo mode (19,200 bps)  
in its handshaking process. The bits that are used in the rate sequence for  
V.32terbo can cause handshaking failure.  
61  
 
User Guide for Series II Modems  
The #V command gives the user the option of including V.32terbo as  
part of the handshaking process in both Orignate and Answer modes.  
Entering AT#V0&W0<CR> includes the V.32terbo mode in  
handshaking. Entering AT#V1&W0<CR> disables the Series II Modem  
336 from using V.32terbo mode in the handshaking process (default).  
Async/Sync Mode Switching &M  
This command can be used to set the on-line mode to either  
synchronous or asynchronous. AT&M0 will set the Series II Modem to  
Asynchronous mode, and all communications will be asynchronous in  
both On-line and Command modes. AT&M1 causes the Modem to com-  
municate asynchronously when in Command mode and switch to syn-  
chronous mode while on-line. The modem defaults to &M0  
(asynchronous communications) on reset or power-up.  
Synchronous Transmit Clock Select &X  
The &X command selects the Synchronous Transmit Clock Source in  
conjunction with DIP-Switch #11. DIP-Switch #11 in the UP position  
enables External clocking. DIP-Switch #11 in the DOWN position  
enables Internal clocking (default position). External clocking is when  
the DTE provides transmit clocking to the modem on pin 24 of the  
RS232C interface.  
&X0 is the default setting, which allows DIP-Switch #11 to control  
Internal/External Clocking (default Internal). Internal clocking is  
when the modem provides transmit clock to the DTE on pin 15 of the  
RS-232C/V.24 interface. The &X1 command overrides DIP-Switch #11  
and selects External clocking. If DIP-Switch #11 is UP (External  
clocking), you can not override Internal clocking. &X2 enables Slave  
Clocking. The &X2 Command causes the Series II Modem to generate  
the transmit clock timing (pin 15) from the receive clock (pin 17) from  
the DTE (therefore 15 and 17 are the same). In this mode (Slave  
Clocking), all timing is controlled by the receive clock.  
62  
 
Chap5:CommandModeter
5.4.5 Command Response (Result Code)  
Commands  
Echo Command Mode Characters E  
If the Series II Modem is connected to a full-duplex computer, it may  
be necessary for the modem to be configured to echo back characters  
entered while in the Command Mode in order for them to be displayed.  
The E command is used to configure the Command Mode echo, with  
ATE0 disabling the echo and ATE1 enabling the echo (default).  
Result Codes Enable/Disable and No Response Answer Q  
The Q command enables or disables Result Codes and the No Response  
Answer mode of operation. Result Codes may be disabled altogether in  
certain applications, such as computer-controlled auto dialing, using  
the Q command. ATQ1 disables Result Code transmissions. ATQ0 (or  
ATQ) enables Result Code transmission.  
Regarding No Response Answer, you may want the answer mode  
handled without responses and echo turned off, but want the originate  
mode still intelligent. This is called the No Response Answer mode.  
ATQ2 selects the No Response Answer mode. If you do not select any  
mode, the factory default setting (enable Result Codes) is automatically  
selected.  
Result Codes ("Series II" or "Standard AT") &Q  
The Series II Modem gives you a choice between the Series II Result  
Codes, and Result Codes that more closely match the standard AT  
command set responses (see section 5.3).  
AT&Q1 selects AT responses with no Reliable/Compression  
modifiers. With this command, the terse result code for CONNECT 2400  
is 10.  
AT&Q0 selects Series II responses with Reliable/Compression  
modifiers. With this command, the terse result code for CONNECT 2400  
is 9.  
63  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Result Codes (Verbose/Terse) V  
The V command controls whether the Series II Modem’s result codes  
are displayed as word (“verbose”) or single digit (“terse”) messages.  
For example, if after dialing, no carrier signal is detected, the resulting  
message can be displayed either as NO CARRIER, or as the digit 3.  
Entering ATV0 (or ATV) causes the Modem to display the Result Codes  
as digits, while ATV1 displays them as words. If you do not select a  
method, the factory default setting causes the modem to display Result  
Codes as words.  
Result Codes (Basic and Extended) and Call Progress  
Selection X  
The X Command is used to select one of two possible dialing methods  
(“dumb” or “smart”), and to select various response combinations related  
to these methods. You can choose to have certain responses suppressed,  
or whether or not you want speed indications along with the CONNECT  
responses. You can also pick and choose certain responses in order to  
match up with “Standard AT” responses. (Refer to Appendix G for a  
summary of Result Codes.)  
The Series II Modem provides “Basic” and “Extended” Result Code sets.  
The difference between the two is the Basic set provides one response  
(CONNECT) to indicate a connection, while the Extended set provides  
several responses for different speeds (CONNECT, CONNECT 2400,  
CONNECT 4800, CONNECT 9600, CONNECT 14400, CONNECT 19200,  
CONNECT 21600, Etc.).  
When the Extended set is chosen, you also have the option of matching  
them up with Standard AT 2400 response code sets, by including or not  
including the BUSY and/or NO DIAL TONE responses while excluding  
the DIAL TONE response. The X command is used to select which  
responses are provided.  
64  
 
CHAPTER 5: Command Mode  
Regarding the Series II Modem’s method of dialing, the Modem can  
detect standard dial tones and busy signals. This capability (“smart  
dialing”) allows the modem to wait for a dial tone, and when one is  
detected, to begin dialing immediately.  
The Modem also can detect a distant busy signal if, after dialing, it  
reaches a busy number. This is useful because it allows the modem to  
immediately abandon a call, rather than wait 45 seconds for a carrier  
signal that will never come. S-Register S7 defines the wait for carrier  
time (refer to Chapter 6).  
The Series II Modem gives you a choice between the wait-for-dial-tone  
(“smart”) method we just described, and blind (“dumb”) dialing, where  
instead of detecting actual dial tones, the modem relies on timed  
pauses. When the wait-for-dial-tone method is chosen, the busy signal  
detection capability is also activated. The X command is also used to  
select which dialing method is used.  
Five different X commands are available (X0 through X4), with five  
different effects on the Modem’s Result Codes.  
X0  
Provides the basic (short) result codes and provides  
“dumb” dial capabilities.  
X1  
Provides the extended result codes and provides “dumb”  
dial capabilities.  
The remaining X commands affect Call Progress, and turn on Extended  
Result Codes.  
X2  
Looks for dial tone only and will not provide a busy  
response.  
X3  
X4  
Looks for busy only and not look for dial tone.  
Looks for dial tone and for busy.  
The factory default setting is X0, which selects Basic Result Codes  
and the blind (“dumb”) method of dialing.  
65  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
5.4.6 Phone Line Conditioning Commands  
Guard Tones &G  
The &G command is used to control the presence or absence of guard  
tones from the transmitter when in Answer mode, at either 1200 or  
2400 bps. Guard tones are used in Europe and other areas for the  
modem to function in the telephone systems. Guard tones are not used  
in the United States. &G0 (default), turns off CCITT guard tones. &G1  
turns on 550 Hz guard tones. &G2 turns on 1800 Hz guard tones.  
Phone Line Monitoring Speaker M  
The Series II Modem has an internal on-board speaker, which functions  
like the speaker in a telephone handset, to enable you to monitor  
phone line activity. The M command can be used to determine when  
the speaker is operational.  
Entering ATM0 disables the speaker completely, while ATM1 causes the  
speaker to be on only until a carrier signal is detected. ATM2 causes the  
speaker to remain on at all times. ATM3 causes the speaker to be on  
during dialing and off during handshake. ATM1 is the default setting,  
and the one that should be used in most applications.  
Enable or Disable Recognition of Remote Digital Loop  
Signal &T  
The Series II Modem has several self-test features (covered in Chapter  
8). The tests are activated with different U commands, such as ATU1,  
and so forth. The &T command is a phone line conditioning command  
that enables or disables the modem’s ability to recognize the Remote  
Digital Loop (RDL) test signal.  
The AT&T4 command lets the Modem respond to a RDL signal, and  
places itself in digital loop. The AT&T5 command causes the modem  
to ignore the RDL signal. The factory default is &T5.  
Enable/Disable Trelis Coded Modulation #T  
This command enables or disables the Trellis Coded Modulation of the  
Series II Modem. There is usually no need to disable (turn off) Trellis  
66  
 
CHAPTER 5: Command Mode  
codings except under an unusual line condition called impulse noise.  
AT#T0 turns Trellis coding off and AT#T1 turns Trellis coding on  
(factory default).  
Fallback Modes When On-Line #F  
If line conditions deteriorate, the Series II Modem automatically drops  
its transmission speed (“fallback”). The #F command controls the  
different ways the Modem falls back. During operation, if the error rate  
becomes too great, the modem performs a retrain. If after the retrain,  
the error rate is still too high for 33600 bps operation, the modem  
initiates a retrain at 4800 bps. If after the first retrain the modem  
returns on line at 33600 bps, the modem then starts a counter and a  
timer. If three retrains occur within a two minute period, the modem  
falls back to 4800 bps.  
Entering AT#F0 (or AT#F) allows no fallback when on-line. AT#F1  
allows the Modem to fallback (based on the error rate or if three  
retrains have occurred within a two minute period) from 33.6K to 31.2K  
to 28.8K to 26.4K to 24K to 21.6K to 19.2K to 16.8K to 14.4K to 12K to  
9.6K to 4.8K bps. The AT#F2 command enables incremental fall back  
from 33.6K to 4.8K, but also enables incremental fall forward (from  
4.8K to 33.6K) if the phone line improves. AT#F2 is the factory default  
setting.  
Enable/Disable Lowspeed Fast Connect $FC (336+ Only)  
With the Series II Modem 336+ (MD1640A), entering  
AT$FC0&W0<CR> sets up the data pump so that it will not transmit a 5  
second 2100 Hz signal. Entering AT$FC0&W0<CR> allows the modem  
to transmit a 5 second 2100 Hz signal and is the factory default.  
Cleardown at Disconnect &CD  
The &CD command is used for control of cleardown at disconnect in  
V.32, V.32bis, V.34 and V.34 enhanced modes.  
A cleardown usually adds 1-2 seconds to the time it takes for the modem  
to go on-hook after a disconnect. A cleardown makes a disconnect by  
the remote modem easier to detect and a subsequent re-connection  
more likely. Enter AT&CD0&W0<CR> to execute a cleardown at  
disconnect (default); and enter AT&CD1&W0<CR> to disable the  
cleardown function.  
67  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Auto Speed Detect #A  
The function of the #A command is to detect and select the operational  
data rates (the “starting” speeds) with which the Series II Modem uses  
for initial handshake and speed selection.  
Remember, this command does not control the originating data rate of  
the modem (that is done by the Modem Baud Rate command $MBn),  
but only the Answer mode “starting” speeds. Entering  
AT#A0 (or AT#A) causes the Modem to operate starting at 33,600 bps,  
with fallback to 28,800 to 19,200 to 14,400 to 9600 to 4800 to 2400 to  
1200 and to 300 bps. Entering AT#A1 causes 33,600 bps operation only.  
Entering AT#A2 causes the modem to operate at starting speeds of  
33,600 bps, with incremental fallback to 28,800, 19,200, 14,400, 9600  
and 4800 bps. The AT#A3 command causes the modem to begin  
operation as a V.22bis modem at 2400 bps, with fallback to 1200  
to 300 bps. AT#A0 is the factory default value.  
5.4.7 RS232C Interface Control Commands  
Carrier Detect Control &C  
The &C command allows you to control the status of the Carrier Detect  
signal (CD, Pin 8) on the RS232C line. You have four choices.  
You can force the signal high, or allow it to act normally, or force the  
modem to reset when CD drops, or set it to stay high until the modem  
disconnects, go low momentarily, and then go high again. The last  
option is useful with some CBX phone systems and mainframe front  
ends, which require CD to act in this manner.  
To allow CD to act normally, enter the command AT&C1 (the factory  
default setting). To force CD on, enter AT&C0. To reset the modem to  
its current parameters when CD drops, enter AT&C4. To set up CD so  
that it drops for one second on disconnect and then comes up again,  
enter AT&C2. (If you want the drop time to be something other than  
one second, use S-Register S24 to change this value. Refer to the  
Chapter 6 instructions for S24.)  
68  
 
CHAPTER 5: Command Mode  
Data Terminal Ready Control &D  
Data Terminal Ready (DTR) on Pin 20 of the RS232C interface is  
required in order for the Series II Modem to operate. A high DTR  
signal tells the modem that the device to which it is connected is active,  
or "ready" to communicate through the modem. If the signal is not  
being provided on the RS232C interface, you can force DTR high with  
DIP-Switch #1 (Chapter 9).  
DTR has some other Modem functions. DTR can be used to trigger a  
dialing sequence, called DTR Dialing. The condition of DTR can also  
be used to cause the modem to reset to its default parameters, just as if  
you had given the modem an ATZ command. To do this, enter the  
command AT&D3 and hit RETURN.  
The modem will now reset itself whenever DTR is dropped from On to  
Off, and will also go on-hook (hang up) if it is on-line.  
Entering AT&D0 or AT&D causes the Modem to ignore DTR. Entering  
AT&D1 causes the modem to go on-hook (hang up) with loss of DTR.  
The modem enters Command mode when DTR goes high again. Auto-  
answer is disabled while DTR is low. Entering AT&D2 causes the modem  
to go on hook with loss of DTR. The modem enters command mode  
when DTR goes high again.  
Clear to Send Control &R  
The &R command allows you to control the Clear to Send signal (CTS,  
Pin 5) on the RS232C interface. You have three choices. You can force  
the CTS signal high, allow it to act normally, or set it to stay high until  
the modem disconnects, go low momentarily, and then go high again.  
The last option is useful with some CBX phone systems and mainframe  
front ends, which require CTS to act in this manner.  
To allow CTS to act normally, enter the command AT&R0. To force  
CTS on, enter the command AT&R1 (this is the factory default setting).  
When the modem goes on-line, CTS still provides flow control. To set  
up CTS so that it drops for one second on disconnect and then comes  
up again, enter the command AT&R2. (If you want the drop time to be  
something other than one second, use S-Register S24 to change this  
value. Refer to Chapter 6).  
69  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Data Set Ready Control &S  
The &S command allows you to control the status of the Data Set Ready  
signal (DSR, Pin 6) on the RS232C interface. You have three choices.  
You can force the signal high, allow it to act normally, or set it to stay  
high until the modem disconnects, go low momentarily, and then go  
high again. The last option is useful with some CBX phone systems  
and mainframe front ends, which require DSR to act in this manner.  
To allow DSR to act normally, enter the command AT&S1 (the default  
setting). To force DSR on, enter the command AT&S0. To set up DSR  
so that it drops for one second on disconnect and then comes up again,  
enter AT&S2. (If you want the drop time to be something other than one  
second, use S-Register S24 to change this value. Refer to Chapter 6.)  
CTS/RTS Interaction Control &RF  
In typical operation, Clear to Send follows Request to Send when the  
modem is on-line. In other words, if RTS goes off, CTS goes off in  
response. The &RF0 command enables CTS to follow RTS. In some  
applications, however, it may be necessary for CTS to operate indepen-  
dently of RTS. &RF1 allows CTS to operate independently regardless  
of the state of RTS, and is the factory default. If this is the case, refer  
to the &R command for control of the Clear to Send signal.  
DSR/CD Interaction Control &SF  
In typical applications, Data Set Ready (DSR) follows Carrier Detect  
(CD). &SF0 enables DSR to follow CD, and is the factory default. &SF1  
enables DSR to operate independent of CD. If this is your application,  
refer to the &S command for control of the Data Set Ready signal.  
5.4.8 Error Correction Commands  
You can use AT commands to place your Series II Modem one of three  
V.42 (error correction) modes of operation. These are the Normal,  
Auto-Reliable, and Reliable modes.  
70  
 
CHAPTER 5: Command Mode  
Normal Mode &E0  
In Normal mode of operation, the Series II Modem’s V.42 error correc-  
tion capabilities are disabled, and the modem functions as a non-error-  
correcting modem.  
Auto-Reliable Mode &E1  
In Auto-Reliable mode during the handshaking procedures at the start  
of the on-line connection, the Series II Modem automatically  
determines whether or not the modem with which it is communicating  
is using V.42 error correction. If the Modem determines that the other  
modem is using V.42, it switches itself into MNP or LAPM Reliable  
(V.42) mode and its error-correction capability is enabled. If it is deter-  
mined that the other modem is not using V.42, the Modem remains in  
Normal mode, without error correction. The default setting is Auto-  
Reliable mode (&E1).  
The method the Modem uses to determine if the modem it calls is a  
V.42 modem involves the use of a “Link Request”.  
When the Series II Modem is in Auto-Reliable mode and originates a  
call, it goes through normal handshaking procedures just like any dial-  
up modem. After establishing the on-line connection, the Modem  
transmits a Link Request message to the answering modem. (The Link  
Request message is generally about 33 coded characters.) If the  
answering modem replies with an appropriate V.42 acknowledgment  
response, the Modem switches into Reliable mode. Otherwise it stays  
in Normal mode. This V.42 Link Request handshaking procedure  
generally takes about five seconds.  
When operating in V.42 Reliable mode, the Series II Modem uses its  
memory, or buffer, to store data as it is received. During periods of  
error-caused retransmissions or compression slowdowns, this buffer  
may fill up. To prevent buffer overflow and subsequent loss of data, the  
modem uses "flow control" to signal the computer attached to its RS232C  
port that the modem buffer is close to being full. This causes the com-  
puter to pause in its data transmission until the modem is able to empty  
its buffer sufficiently to accept more data, at which time the modem  
signals the computer that it may resume transmission. (Flow Control is  
discussed in section 5.4.9.)  
71  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Reliable Mode &E2  
In Reliable mode, the Series II Modem uses its V.42 error correction  
capabilities during all transmissions, and must be connected to another  
modem with a similar protocol activated (MNP or LAP-M).  
V.42 Mode Select #L  
The V.42 standard implements both MNP Class 3 & 4 and LAP-M error  
correction methods. The V.42 Mode Select command (#L) selects which  
type of error correction (MNP or LAP-M) your Series II Modem uses for  
transmissions.  
The various #L command options are as follows.  
#L0 Command  
The #L0 Command allows a pair of  
modems to negotiate which V.42 mode  
(MNP or LAP-M) will be used in their  
transmissions.  
Originate Mode  
a. If both modems have LAP-M capability,  
the modems use LAP-M mode.  
b. If one or both modems do not have LAP-  
M capability and both have MNP, the  
modems use the MNP mode.  
#L0 Command (cont'd)  
Answer Mode  
a. The answering modem responds to either  
an MNP Link Request or LAP-M Originator  
Detection Pattern (ODP) signal depending  
on which the originating modem issues.  
#L1 Command  
#L2 Command  
The #L1 Command sets your modem to  
MNP error correction and disables LAP-M.  
This command is for Originate mode only.  
In Answer mode, the modem still accepts  
MNP or LAP-M.  
The #L2 Command sets your modem to  
LAP-M error correction, and disables MNP.  
72  
 
CHAPTER 5: Command Mode  
This command is for Originate mode only.  
Answer mode still accepts MNP or LAP-M.  
#L3 Command  
In the prior commands, the modems use a  
two phase process to establish a V.42  
connection (detection to establish whether  
the remote modem is also error correcting,  
and then protocol establishment to deter-  
mine parameters and to establish the error  
correction connection). If you know that  
the other modem is a V.42 error correcting  
modem, and you wish to use LAP-M, the  
#L3 command disables the detection phase  
and goes directly to protocol establishment.  
Both modems must have #L3 in effect.  
Auto-Reliable Buffering $A  
In Auto-Reliable mode, the modem is given four seconds to establish a  
Reliable connection. After this four-second period, the modem drops to  
Normal mode. Any data which is received during this period is typically  
discarded. The $A command can be used to cause the modem to buffer  
(save) data that is received during this Auto-Reliable time-out period.  
This data will then be output by the modem after the  
CONNECT message.  
AT$A0 = Discard data received during auto-reliable time period.  
AT$A1 = Buffer data received during auto-reliable time period.  
The factory default is $A0.  
Enable/Disable Auto Reliable Fallback Character $F  
In Auto-Reliable mode, the modem is given four seconds to establish a  
Reliable connection. If a single CARRIAGE RETURN is received from  
the remote modem during this four second period, the Auto-Reliable  
modem assumes that the remote modem is not in Reliable mode and  
drops to Normal ( non-error correcting) mode. The CARRIAGE  
RETURN is the only character which causes the modem to drop to  
Normal mode. Any other character will either be buffered or discarded.  
73  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
The $F command can be used to disable this fallback-to-Normal-due-to-  
CARRIAGE-RETURN feature.  
The Auto-Reliable fallback character ($F) and Auto Reliable buffering  
($A) commands can be used together to cause the modem to buffer all  
data received up until the CARRIAGE RETURN, and then drop to  
Normal mode. All data received will then be output following the  
CONNECT message.  
AT$F0 = Do not fall back to Normal if CARRIAGE RETURN  
received.  
AT$F1 = Fall back to Normal mode if CARRIAGE RETURN  
received.  
The factory default is $F0.  
Retransmit Count $R  
If errors are received during a Reliable connection, the modem  
re-sends the block of data which contained an error. With the $R0  
command, if another error occurs, the block will be re-sent again. The  
modem counts the number of times that a data block is re-sent. If the  
same block of data is resent 12 times and still has not been received  
properly, the modem assumes that the transmission line is unsuitable  
for transmission, and abort the connection.  
This retransmit counter is disabled by the $R1 command. When the  
retransmit counter is disabled, the modem keeps trying to send data  
and will not abort, no matter how many times the same block is resent.  
AT$R0 = Disconnect if retransmit count is exceeded.  
AT$R1 = Do not disconnect due to retransmits.  
The factory default setting is $R0.  
74  
 
CHAPTER 5: Command Mode  
V.42 Error Correction/300bps $E  
At 300 bps, error correction is not typically used. $E1 lets the Series II  
Modem function at 300 bps in either Normal (&E0), Auto-Reliable  
(&E1) or Reliable (&E2) mode. $E0, which is the Modem’s default,  
disables 300 bps/V.42 error correction altogether.  
AT$E0 = No V.42 Error correction at 300 bps.  
AT$E1 = V.42 Error Correction at 300 bps.  
The factory default setting is $E0.  
5.4.9 Flow Control Commands  
Flow control refers to the techniques used by computer devices to stop  
and restart the flow of data to and from each other. Flow control is  
necessary so that a device does not receive more data than it can  
handle. In the case of the Series II Modem, there is a need for flow  
control in both directions. As illustrated on the next page, flow control  
for data passing from your computer to the modem is called Modem-  
Initiated Flow Control and flow control for data passing from the  
modem to your computer is called Computer/Terminal-Initiated  
Pacing.  
The Series II Modem supports both hardware and software Modem  
Initiated Flow Control. On the Computer/Terminal-Initiated Pacing  
side, it supports hardware and software flow control, and a special  
®
version used by Hewlett-Packard compatible systems called ENQ/ACK  
Pacing. The Modem allows hardware and software pacing to be passed  
through the modem to the other end of the link so that your computer  
or terminal can control data start/stop activity through your modem.  
This is called Xon/Xoff Pass-Through. To state it simply, “Flow Control”  
is something the modem does to the computer, while “Pacing” is  
something the computer does to the modem.  
75  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Modem-Initiated Flow Control  
RS/232/V.24  
data flow  
Computer or  
Terminal  
Modem  
Computer-Initiated Flow Control  
Computer,  
Terminal, or  
Printer  
RS/232/V.24  
data flow  
Modem  
Figure 5-2. Flow Control and Pacing  
Hardware Flow Control &E4  
With Hardware Flow Control, the modem uses its RS232C interface to  
control the flow of data from the computer or terminal to which it is  
attached. The CTS (Clear to Send) signal on Pin 5 of the RS232C  
interface is brought low to stop the flow of data, and is brought high  
to restart it. When you select Hardware Flow Control as your Modem  
Initiated Flow Control method, you will also be selecting it for Pacing.  
The difference between the two, however, is that Modem-Initiated Flow  
Control uses the Pin 5 CTS output signal, while Pacing uses the Pin 4  
RTS input signal.  
Modem commands are used to select the method of flow control used  
by the Series II Modem when its error correction capabilities are used.  
These commands are covered in Section 5.4.9. If neither method is  
selected, the modem defaults to no flow control (&E3).  
76  
 
CHAPTER 5: Command Mode  
Xon/Xoff Flow Control &E5  
Xon/Xoff is the most commonly used method of flow control. Under  
this method, control characters known as “Xon” and “Xoff” are inserted  
by the modem into the data to start and stop the flow of data from the  
computer or terminal to which the modem is attached. Xoff, which is a  
Control-S, stops the flow of data, and Xon, which is a Control-Q, restarts  
it. With regard to Binary Data, Xon/Xoff flow control is not recom-  
mended because an Xoff character may be part of the data and would  
trigger an Xoff of the modem or software package, which would halt  
data flow.  
Xon/Xoff Pass-Through &E7  
So far, you have had three choices to make regarding pacing:  
1. You can set the modem to respond to Xon/Xoff pacing.  
2. You can set the modem to respond to RTS pacing.  
3. You can set the modem to ignore pacing completely.  
Well, we’re not done with pacing yet. There’s another choice you can  
make (which actually can apply to both pacing and modem-initiated  
flow control, although it applies mainly to pacing) and that is  
something called “Xon/Xoff Pass-Through.”  
This means that if your modem is set to respond to Xon/Xoff com-  
mands, you can have the modem do one of the following:  
1. The modem responds to the Xon and Xoff pacing commands  
while at the same time allowing these commands to pass through  
the modem and on to the remote location. We call this “Respond,  
Pass-Through”.  
2. The modem responds to Xon/Xoff pacing, but does not allow the  
pacing signals to pass through the modem and on to the remote  
location. We call this “Respond, No Pass-Through”.  
When Xon and Xoff commands are allowed to pass through the  
modem, the computer or terminal at the remote site will receive these  
commands, and depending on how it is configured, the computer or  
terminal may respond to them also.  
77  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
When two Series II Modems are connected in Normal mode (not using  
error correction), Xon/Xoff can be used to control the flow of data  
between the modems. Flow Control can be turned on or off with the  
Normal Mode Modem Flow Control commands. When the modems  
are connected in Reliable mode, a different method of modem Flow  
Control is used, and the commands for Normal Mode Modem Flow  
Control are ignored.  
When you are using Speed Conversion in Normal Mode, you must  
activate the modem’s Normal Mode Modem Flow Control. (Speed  
Conversion is explained in Section 5.4.11.)  
Send Xon/Xoff Characters #X  
The #X phone interface command allows the Series II Modem to send  
either a single or multiple Xoff characters at the modem's buffer full  
level. When the Modem's buffer reaches it's "buffer full" level, the next  
character received causes another Xoff to be sent for every character  
subsequently received by the Modem.  
The AT#X0 command (factory default setting) causes one Xoff to be  
sent until the buffer reaches the Xon level. The AT#X1 command  
causes an Xoff to be sent for every character received after the modem  
reaches its buffer full level.  
Hewlett-Packard ENQ/ACK Pacing &E9  
If the Series II Modem is being used with Hewlett Packard (or similar)  
equipment that employs ENQ/ACK pacing, the modem can be  
configured to respond to ENQ/ACK commands, making it compatible  
with HP systems. Doing so does not affect any other flow control or  
pacing already configured in the modem.  
When configured for ENQ/ACK, the ENQ (Control-E) and ACK  
(Control-F) signals from the HP equipment will be accepted and re-  
sponded to according to Hewlett-Packard protocol.  
Normal Mode Modem Flow Control On &E11  
When two Series II Modems are connected in Normal mode (not using  
error correction), Xon/Xoff can be used to control the flow of data  
between the modems. Flow Control can be turned on or off with the  
Normal Mode Modem Flow Control commands. When the modems are  
78  
 
CHAPTER 5: Command Mode  
connected in Reliable mode, a different method of modem flow control  
is used, and the commands for Normal Mode Modem Flow Control are  
ignored.  
When you are using Speed Conversion in Normal Mode, you must  
activate the modem’s Normal Mode Modem Flow Control. (Speed  
Conversion is explained in Section 5.4.11.)  
Terminal/Computer Initiated Pacing &E13  
As mentioned earlier, the Series II Modem can initiate flow control by  
issuing Xon/Xoff commands or toggling the CTS signal on the RS232C  
interface. The modem can also be configured to react to similar com-  
mands and signals from the computer or terminal to which it is  
attached via the RS232C interface. We refer to the computer or  
terminal initiated flow control as Pacing. When the modem is set for  
Pacing On, the modem will respond to the terminal or computer  
pacing. When the modem is set for Pacing Off, it will ignore pacing.  
In order for the Series II Modem to be set for Pacing On, a modem-  
initiated method of flow control must be previously selected. Once this  
is done, the Modem will respond to either Xon/Xoff commands, or to  
the toggling of the RTS (Request to Send) signal on Pin 4 of the  
RS232C interface, depending on what you selected earlier as your  
Modem-Initiated Flow Control method.  
Maximum Block Size &BS  
The maximum size of Reliable mode data blocks can be controlled with  
the &BS command. MNP 3 sends blocks of 1 to 64 characters. MNP 4  
and 5 typically send blocks of 1 to 256 characters and LAP-M typically  
send 128 characters. For MNP Classes 4 and 5 and for LAP-M, reducing  
the block size to 64 characters may give a smoother flow of data, and  
better throughput on noisy phone lines. Using smaller block sizes over  
good phone lines may cause a slight loss in throughput (speed).  
AT&BS0 = Maximum transmit block size of 64 characters  
AT&BS1 = Maximum transmit block size of 128 characters  
(LAP-M) or 256 characters (MNP)  
The factory default setting is &BS1.  
79  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Asynchronous Word Length Selection $EB (336 Only)  
The Series II Modem 336 (MD1641A) has an 11-bit capacity when  
operating asynchronously. The $EB command selects between 11-bit  
and 10-bit operation. AT$EB1 enables 11-bit format (1 start bit, 8 data  
bits, 1 parity bit, and 1 stop bit). AT$EB0 (default) enables 10-bit  
format (1 start bit, 7 data bits, 1 parity bit, and 1 stop bit). $EB is  
functional in both command and on-line mode. $EB0 automatically  
detects parity when any AT command is issued.  
AT$EB0 = Use 10-bit words  
AT$EB1 = Use 11-bit words  
The factory default setting is AT$EB0.  
Parity Selection #P  
The #P command enables the setting of parity. AT#P0 selects no parity.  
AT#P1 selects odd parity. AT#P2 selects even parity and is the default  
value. Note when setting up your data comm software, it is critical that  
both your remote and local system's parity selection be set identically.  
AT#P0 = no parity  
AT#P1 = odd parity  
AT#P2 = even parity  
The factory default setting is AT#P2.  
80  
 
CHAPTER 5: Command Mode  
5.4.10 Compression, Error Correction, Flow  
Control, Pass-Through and Pacing  
Commands  
The Series II Modem has a variety of commands to control its error  
correction and data compression options. These additional commands  
are listed below. (Remember to precede each command with the AT  
characters.) Factory-default settings are marked with asterisks.  
Normal/Auto-Reliable/Reliable Mode Commands:  
&E0 =  
&E1 =  
&E2 =  
Normal Mode  
Auto-Reliable Mode*  
Reliable Mode  
Modem-Initiated Flow Control Commands:  
&E3 =  
&E4 =  
&E5 =  
Disables flow control (no flow control)  
Hardware flow control (CTS on/off and RTS on/off)*  
Xon/Xoff flow control  
Xon/Xoff Pass-Through Commands:  
&E6 =  
&E7 =  
Modem responds to Xon/Xoff characters, but does not  
allow Xon/Xoff characters to pass through to remote  
site.*  
Modem responds to Xon/Xoff characters, and allows  
them to pass through to remote site.  
#X0 =  
#X1 =  
Selects single Xoff character until Xon level returns*  
Selects multiple Xoff characters after buffer levels is  
full.  
*Factory-default setting.  
81  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Enq/Ack Pacing Commands:  
&E8 =  
&E9 =  
Enq/Ack method of pacing off*  
Enq/Ack method of pacing on  
Normal Mode Modem Flow Control Commands:  
&E10 =  
&E11 =  
Normal Mode Modem Flow Control off*  
Normal Mode Modem Flow Control (Xon/Xoff) on  
Computer-or Terminal-Initiated Flow Control (Pacing) Commands:  
&E12 =  
&E13 =  
Pacing off*  
Pacing on (either RTS on/off or Xon/Xoff depending on  
the setting of &E4 or &E5).*  
Data Compression Commands:  
&E14 =  
&E15 =  
Data Compression disabled  
Data Compression enabled*  
*Factory-default setting.  
5.4.11 Speed Conversion Commands  
Speed conversion is a necessary part of data compression since data  
must be presented to the modem faster than it can handle data, if data  
compression is to be effective.  
Speed conversion allows the Series II Modem to communicate at one  
speed over the phone line, and at another speed at the RS232C  
interface. The speed (also referred to as “data rate” or “baud rate”) can  
be fixed at the RS232 interface independently of the baud rate of the  
on-line transmissions.  
In addition to data compression, another popular application for speed  
conversion involves an auto-answer Series II Modem connected to a  
computer that does not have autobaud capability. This means that the  
82  
 
CHAPTER 5: Command Mode  
computer must be set at a fixed baud rate, regardless of whether the  
modem is communicating over the phone line at 300, 1200, 2400, 9600,  
14,400,19,200, 24,000, 28,800 or 33,600 bps. In this application, speed  
conversion allows the modem to match its speed to that of the calling  
modem, while at the same time communicating with the attached  
computer through its RS232C port at a fixed baud rate, which can be  
pre-selected at 300, 1200, 2400, 4800, 9600, 19,200, 38,400, 57,600 or  
115,200 bps.  
Speed Conversion $BA  
When using speed conversion, you must set the modem so that it does  
not adjust its speed at the RS232C serial port, even if the modem does  
adjust its data rate. To turn Speed Conversion ON, enter the command  
AT$BA0&W0 and hit RETURN.  
To turn Speed Conversion OFF, enter AT$BA1&W0 and hit RETURN.  
The modem will now match its RS232C speed to that of the computer,  
and will adjust its speed to any changes in the computer’s speed in  
Originate mode, or to the speed of the originating modem in Answer  
mode. The speed at which the modem communicates over the phone  
line will always be the same as the speed at which it communicates via its  
RS232C serial port.  
Modem Baud Rate $MB  
The $MB command presets the Series II Modem’s transmission baud  
rate for originate operations, (i.e., the speed of the modem’s transmis-  
sions over the telephone lines when originating a call). With speed con-  
version, this transmission speed can be a different baud rate than the  
serial port speed.  
When the Series II Modem receives (answers) a call from another  
modem, it automatically switches its phone line transmission speed to  
match the calling modem. However, if the Modem originates a call to  
another modem that is unable to connect at the baud rate of the  
Modem, it automatically drops to a lower baud rate in an attempt to  
match the speed of that modem. For example, if the Modem is set for  
19,200 baud and calls another modem that has a top speed of  
2400 baud, it drops to 2400 baud.  
83  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
The command to set the Modem Baud Rate is AT$MBn, where n can  
be 300, 1200, 2400, 4800, 9600, 14,400,19,200, 28,800 or 33,600 bps as  
listed below:  
AT$MB300  
=
=
=
=
=
=
=
=
=
300 bps  
AT$MB1200  
AT$MB2400  
AT$MB4800  
AT$MB9600  
AT$MB14400  
AT$MB19200  
AT$MB28800  
AT$MB33600  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
14400 bps  
19200 bps  
28800 bps  
33600 bps  
The factory default is 33600 bps.  
Serial Port Baud Rate $SB  
The $SB command presets the speed of the Series II Modem’s serial  
(RS-232C) port, in both Originate and Answer modes. Speed  
conversion allows you to set this serial port baud rate at a fixed speed  
of up to 115,200 bps, regardless of the modem’s transmission speed  
setting.  
In order for this command to be effective, the modem’s Speed  
Conversion feature must first be turned off with the $BA command.  
When Baud Adjust is on, the Modem automatically adjusts its serial port  
baud rate to match the speed of the computer or terminal it is connect-  
ed to, as soon as it receives its first AT command. However, in many ap-  
plications, such as automatic answer, the modem may not receive AT  
commands, in which case it is very useful to be able to preset the serial  
port baud rate with this $SB command.  
In addition to setting the Modem’s serial port speed, this command also  
sets the speed at which the modem issues Command mode responses.  
The Modem will accept AT commands at any speed, regardless of the  
speed preset by the $SB command. If the modem receives such a com-  
mand at a speed that is different than the preset speed, the modem  
switches its serial port baud rate to match the new AT command speed,  
although the baud rate value stored by the $SB command remains the  
84  
 
CHAPTER 5: Command Mode  
same. This provides you with a convenient way to switch the serial port  
speed, and still make it easy to go back to the original speed automati-  
cally the next time the modem is powered up or reset with an ATZ  
command.  
The command to set the Serial Port Baud Rate is AT$SBn, where n can  
be 300, 1200, 2400, 4800, 9600, 19,200, 38,400, 57,600 or 115200 bps as  
listed below:  
AT$SB300  
=
=
=
=
=
=
=
=
=
300 bps  
AT$SB1200  
AT$SB2400  
AT$SB4800  
AT$SB9600  
AT$SB19200  
AT$SB38400  
AT$SB57600  
AT$SB115200  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
19,200 bps  
38,400 bps  
57,600 bps  
115,200 bps  
The factory default is 115,200 bps.  
Note: Some serial ports, particularly those in older PC-compatible  
computers, may limit the performance of a higher speed modem like  
the Series II Modem (see Chapter 3). The limiting factor is a circuit  
called a Universal Asynchronous Receiver/Transmitter, or UART. All  
data from your modem flows through it. 8250, 16450, and 16550 are  
UARTs typically used in PC-compatible computers. The 8250 is  
unreliable above 9,600 bps and the 16450 is unreliable above 19,200  
bps. The 16550 UART, however, is reliable to at least 115,200 bps. With  
V.42bis data compression enabled, the Modem can achieve throughputs  
approaching 115.2K (depending on line quality and file content).  
5.4.12 Immediate Action Commands  
Help Screens $H  
The Help command is designed to give you short explanations on how  
to use each Series II Modem command. The Help command can be  
quite useful if your manual is not handy and you are in the middle of a  
communications session. Although the explanations are quite abbreviat-  
ed compared to those in this manual, they should prove to be helpful  
reminders when needed.  
85  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
At the time of this writing, we have three screens of Help information  
(Screen #1, #2 and #3), and more screens may be added in the future.  
The Help commands are structured so that you can call up one of three  
Help screens, as follows:  
AT$H1 = Help Screen #1  
AT$H2 = Help Screen #2  
AT$H3 = Help Screen #3  
Inquiry for Product Code I  
Some systems or software packages automatically check the  
“identification” of the modem with which they are communicating, by  
using the I command. This “read” command lets the software to deter-  
mine the type of modem with which it is communicating.  
When ATI or ATI0 is entered, the Series II Modem responds with 247.  
When ATI1 is entered, the modem responds with a three-digit code  
indicating the firmware version number. When ATI2 is entered, the  
modem responds with MD1641A if it’s a 336 model or MD1640A if  
it’s a 336+ model.  
Windows 95 Autodetect Inquiry I9  
This read command permits a Windows 95 operating system to query  
the Series II Modem's characteristics. When ATI9<CR> is entered, the  
symbols BA 28800 FAX CT (336 model) or BL 28800 FAX CT (336+  
model) are displayed; which indicates to the Windows 95 system that  
your particular modem is a Series II Modem 336 or 336+, 28,800 bps, fax  
Class 2 capable modem. With autodetect support in your Modem, your  
PC can automatically allocate resources and configure it and other  
devices. The Modem implements autodetect capability in the form of  
a single .INF (Information) file that specifies AT Command mode and  
Result Code "Registry Keys" that are specific to your Modem.  
86  
 
CHAPTER 5: Command Mode  
Listing Current Operating Parameters L5 L7  
The L5 and L7 commands list the current operating parameters of your  
modem. This information can be very useful when you are changing  
communications software or when you are changing modem default  
settings.  
The command to list the Series II Modem’s current operating parame-  
ters is ATL5 for the basic parameters. Entering ATL7 lists additional  
parameters on the Modem.  
Listing S-Register Values L6  
Entering ATL6 lists the current values stored in the modem’s S-Register.  
This information can be very useful if you wish to change S-Register  
values. (Refer to Chapter 6 for more information on S-Registers).  
Listing On-Line Diagnostics L8  
The L8 command displays the current on-line CONNECT status of the  
Series II Modem. This display can be printed and used as a modem  
status report or as diagnostic information (such as when calling Tech  
Support). To activate this command first type +++AT<CR>(on-line escape  
command while maintaining command mode), then type ATL8. What then  
displays on your monitor is your modem's current on-line condition  
(e.g., Link Type, Line Speed, Serial Speed, Type of Error  
Correction/Data Compression, Number of past Retrains, etc.).  
See Figure 5-2 on the next page for a sample screen as displayed  
through a Windows based terminal program.  
87  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
File Edit Setup Perform Transfer Windows  
Help  
Feb29, 96 4:50pm MEWDEF  
Connected to device  
00:04:55  
DCD  
CTS  
DSR  
024  
2A71  
0213  
ONLINE DIAGNOSTICS  
L**IN*K*****T*Y**PE  
LINE  
SERIAL SPEED  
ERROR CNTRL/COMPRESS  
FALL  
DATA  
***********  
28800/26400  
V.34  
SPEED  
19200  
LAPM  
BACK/FORWARD LOCALLY ENABLED  
FORMAT  
ASYCHRONOUS  
SYMBOL RATE(SYMETRIC) 3429/3429  
CARRIER FREQUENCY  
TRELLIS ENCODER  
PRECODING  
1959/1959  
4D 16-STATE/4D 16-STATE  
OFF/OFF  
LINE  
TYPE  
DIAL UP  
RECV. SIGNAL LEVEL  
TRANS SIGNAL LEVEL  
NUMBER OF RETRAINS  
ROUND TRIP DELAY  
-024.5 dBm  
-011 dBm  
000  
0005 ms  
-028.0/072.0 dBm  
(MEANINGFUL IN V34 AND V32 MODE)  
NEAR/FAR ECHO LEVEL  
F1  
F2  
F3  
F4  
F5  
F6  
F7  
F8  
F9  
F10  
F11  
F12  
Figure 5-2. On-line diagnostics information.  
On or Off Hook H  
You can make the Series II Modem hang up (go On Hook). Entering  
ATH1<CR> brings the line Off Hook, just as if you picked up the  
telephone set. You can hang up by entering ATH0 or ATH (the default  
is 0 when no number is entered).  
Escape Sequences- Entering Command Mode While Still  
On-Line +++AT<CR>  
It is possible to cause the Series II Modem to enter Command mode  
after the modem has gone on-line with a remote modem without  
disconnecting the call. This is done by entering an Escape Code. The  
default Escape Code used by the Modem is three plus signs (+++)  
followed by the letters A and T, up to sixty command characters (most  
typically “H”, to hang up), and a RETURN. The number of command  
characters allowed after +++ AT<CR> , is defined by S-Register S34.  
S-Register S34 defaults to ten command characters.  
88  
 
CHAPTER 5: Command Mode  
When this is done, the modem escapes to Command Mode, executes  
the command (if any), and then remain in Command mode. For  
example, to hang up the modem at the end of a call, enter +++ATH and  
hit RETURN. There is no need to incorporate pauses before and after  
the plus signs, as done in earlier modems.  
BREAK AT<CR>  
The Series II Modem provides an alternative Escape method, using a  
Break signal as the Escape Code. The Break signal allows the start-stop  
DTE (data terminal equipment) to signal the modem without loss of  
character transparency. With this method, a BREAK signal is used  
instead of the three plus signs. The BREAK is followed by the letters A  
and T, up to 60 command characters, and RETURN. When this is done,  
the modem executes that command, but remains in On-Line mode  
unless the command was to hang up and/or reset the modem (an H or  
Z), in which case the modem would be in the Command Mode after ex-  
ecuting that command.  
Escape Sequence Options - Entering Command Mode  
While On-Line %E  
As mentioned, the default escape sequence setting is for the modem to  
respond to the +++ escape method. Optional settings are for the  
modem to respond to the Break method, for the modem to respond to  
either the +++ or the Break Methods, for the modem to ignore both  
methods and not escape, for the modem to respond with no "OK" to  
+++, and for the modem to respond with "OK" to +++. The %E com-  
mand is used to select these options, as follows:  
%E0  
%E1  
%E2  
%E3  
%E4*  
%E5*  
=
=
=
=
=
=
Modem Won’t Escape  
+++ AT<CR> Method (default)  
Break Method  
Either +++ or Break Methods  
No "OK" Response to +++  
"OK" Response to +++  
* The %E4 and %E5 commands enable or disable an "OK" response,  
which is required by some software packages during an escape  
sequence.  
89  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Force Answer Mode A  
You can force the Series II Modem into Answer mode with the modem’s  
A command.  
Entering ATA when in Command mode immediately brings your mo-  
dem off-hook, out of Command mode and into On-Line Answer mode,  
and causes it to transmit its carrier signal over the phone line. If no  
responding carrier tone is received by your modem within forty-five  
seconds (or some other time as determined by S-Register S7), your  
modem stops transmitting its tone, hangs up, and goes back into  
Command mode.  
Exiting Command Mode, Going Back On-Line O  
You can bring the Series II Modem out of Command mode and back  
into On-Line mode by entering ATO (where O is the letter O, not the  
number 0). In this case, the O command reverses what was done by  
entering the Escape Code. The O command will bring the modem into  
the same On-Line mode (Originate or Answer) that it was in prior to  
going into Command mode.  
5.4.13 Line Probe Commands  
Before V.34 negotiation takes place, remote and local modems transfer  
their functional capabilities using modulated calling and answering  
tones; indicating the common capabilities of the modem at each end.  
Once this is done, a probing signal is passed between the modems to  
identify impairments in the telephone channel (e.g., Receive Signal  
Strength vs. Frequency, Noise vs. Frequency and Signal to Noise Ratio  
vs. Frequency). After receiving the results of the probing signal, the  
modem receivers and transmitters begin with the lowest speed and  
move up until reaching the highest speed at which they can exchange  
data. All this occurs in about five seconds.  
There are a number of Line Probe Commands. These commands are  
configurable and can be stored to RAM (via AT&W0).  
90  
 
CHAPTER1: Specifications  
These commands are listed below.  
Enable/Disable Reading of Line Probe Information Commands:  
%DP0  
Do not read Line Probe information from DSP during handshake  
(Default).  
%DP1  
Read Line Probe information from DSP during handshake.  
Format of Line Probe (Graph or Table) Commands:  
%DF0  
Data is displayed in Graph format. Y axis is shown in dBms (Default).  
%DF1  
Data is displayed in Table format. Numeric values are displayed  
150 Hz to 3750 Hz in 75-Hz increments.  
Immediate Action Line Probe Commands:  
To activate these commands first type +++AT<CR> (on-line escape  
command while maintaining command mode), then type the Command  
prefixed by an AT.  
&RP  
This command initiates a retrain that makes the processor read Line  
Probe information. Valid only when on-line in V.34 mode.  
L9 = Displays Signal Strength information.  
L10 = Displays Signal to Noise Ratio information (SNR).  
L11 = Displays noise information.  
91  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
6. S-Registers  
6.1  
Introduction  
Certain Command Mode configurations are stored in memory registers  
called, S-Registers. The S command is used to assign a value to, and to  
read the current value of an S-Register. To assign a value to an S-  
Register, enter the letter S, followed by the S-Register number and an  
equals sign (=), and then a decimal response to the message “ENTER  
THE NEW VALUE IN DECIMAL FORMAT”. To read an S-Register value,  
enter the letter S followed by the S-Register number and a question  
mark (?), then hit RETURN. To verify that the S-Register value was  
entered correctly, enter for example, ATS8? and hit RETURN. You  
should receive a response of the assigned value given to that S-Register.  
Refer to Section 6.2, Reading and Assigning S-Register Values.  
S0  
Number of Rings Until Modem Answers  
Unit:  
Rings  
Range:  
0-255  
Default:  
Description:  
1
S0 defines the number of rings the modem waits  
before answering an incoming call. The default  
value is one ring (Decimal 1), which means that  
the modem answers the call immediately after  
the first ring. The maximum number of rings  
that can be configured is 255. Setting the value  
to zero (0) disables auto-answer completely.  
S1  
Rings Which Have Occurred  
Unit:  
Rings  
Range:  
0-255  
Default:  
Description:  
0
S1 counts the number of rings that have  
occurred. It is a “read” type of register and is  
seldom, if ever, used in typical operation. Each  
92  
 
CHAPTER 6: S-Registers  
time an incoming ring signal is detected, S1  
increases its value by one, up to a maximum of  
255. If you set S1 to a value other than its default  
value of zero, or if the value is increasing with  
rings, this new value remains stored in S1 for  
eight seconds after the last ring is counted, after  
which time the value reverts to zero.  
S2  
Escape Code Character  
Unit:  
Decimal equivalents of ASCII characters  
Range:  
0-127  
Default:  
Description:  
43 (+)  
S2 defines the escape code character. The  
default character is the plus (+) sign  
(43 decimal), but may be set for any ASCII  
character. Setting an S2 value greater than 127  
results in no escape character, and therefore no  
means of entering Command mode from On-  
line mode without breaking the on-line  
connection.  
S3  
Return Character  
Unit:  
Range:  
Decimal equivalents of ASCII characters  
0-127  
Default:  
Description:  
13 (^M)  
S3 defines the character recognized as Carriage  
Return (RETURN) or “Enter”. S3 may be set for  
any ASCII character.  
S4  
Line Feed Character  
Unit:  
Decimal equivalents of ASCII characters  
Range:  
0-127  
Default:  
Description:  
10 (^J)  
S4 defines the character recognized as Line  
Feed. S4 may be set for any ASCII character.  
93  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S5  
Backspace Character  
Unit:  
Decimal equivalents of ASCII characters  
Range:  
0-127  
Default:  
Description:  
8 (^H)  
S5 defines the character recognized as  
BACKSPACE. S5 may be set for any ASCII  
character.  
S6  
Wait Time for Dial Tone  
Unit:  
Seconds  
Range:  
2-255  
Default:  
Description:  
2
S6 sets the time the modem waits after the  
RETURN key is pressed before executing a dial  
command. The default setting is two seconds.  
S7  
Time for Carrier (Abort Timer)  
Unit:  
Seconds  
Range:  
1-255  
Default:  
Description:  
45  
S7 defines the Abort Timer (lack of carrier)  
delay time. The default value is 45 seconds. This  
means that, after dialing, the modem waits for a  
carrier signal for up to 45 seconds and, if none is  
detected, aborts the call. The maximum S7 value  
is 255.  
S8  
Pause Time for Comma  
Unit:  
Seconds  
Range:  
0-255  
Default:  
Description:  
2
S8 sets the length of the pause caused by a  
comma inserted in a dialing command. The  
94  
 
CHAPTER 6: S-Registers  
default setting is two seconds. S8 may be set for  
up to 255 seconds.  
S8 also sets the time the modem waits before  
retrying a call after detecting a busy signal. Some  
computer systems need more than two seconds  
to reset (in which case you should increase the  
value of S8).  
S9  
Carrier Detect Response Time  
Unit:  
100-mSec intervals  
Range:  
1-255  
Default:  
Description:  
6
S9 sets the time delay between when the modem  
first detects a valid incoming carrier signal and  
when the modem turns on its Carrier Detect  
circuit. The default setting is 600 milliseconds  
(six units of 100 mSec each). S9 may be set to a  
maximum of 255 (25.5 seconds).  
S10  
Carrier Loss Disconnect Delay Time  
Unit:  
100-mSec intervals  
Range:  
0-255  
Default:  
Description:  
7
S10 sets the time a carrier signal must be lost  
before the modem disconnects. The default  
setting is 700 mSec (seven units of 100 mSec  
each). Maximum delay is 25.4 seconds (S10 set  
to 254). Setting the S10 value to 255 causes the  
modem to not disconnect with loss of carrier.  
(This S-Register applies at speeds of 2400 bps  
and less.)  
95  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S11  
Tone Dialing:Tone Spacing and Duration  
Unit:  
Milliseconds (mSec)  
Range:  
1-255  
Default:  
Description:  
70  
S11 sets the speed of tone dialing (spacing and  
tone duration times). The default value is  
70 mSec, meaning that each tone is on for  
70 mSec with a 70 mSec pause between each.  
The minimum S11 value allowed by most  
telephone systems is 50 mSec. Very few  
telephone systems can handle anything faster  
than that. The maximum S11 value is 255 mSec.  
S13  
Remote Configuration Escape Character  
Unit:  
Decimal equivalents of ASCII characters  
Range:  
0-127  
Default:  
Description:  
37 (%)  
S13 defines the remote configuration escape  
character (which becomes your modem’s  
remote configuration character). The default is  
three percent symbols (%%%). When the S13  
character is entered three consecutive times  
from a remotely connected site, your modem  
responds with its Remote Configuration  
procedure.  
S15  
Callback Time Delay  
Unit:  
Seconds  
Range:  
10-255  
Default:  
Description:  
20  
S15 defines the time delay between Callback  
attempts after initial passwords have been  
exchanged between modems. Refer to Chapter 7  
for Callback Security information.  
96  
 
CHAPTER 6: S-Registers  
S16  
Callback Attempts  
Unit:  
Range:  
Default:  
Description:  
Attempts  
1-255  
4
S16 defines the number of attempts allowed  
after initial passwords have been exchanged  
between modems.  
S17  
Changing Break Time  
Unit:  
10-mSec intervals  
Range:  
0-250  
Default:  
Description:  
250  
S17 defines the break time (space) sent to the  
local PC. The default is set for a 250-mSec  
(2.5-second) break. The break time can be  
changed in 10-mSec increments by increasing  
or decreasing the value of S17.  
S18  
Automatic Leased Line Restoral (336+ Only)  
Unit:  
Minutes  
Range:  
10-255  
Default:  
Description:  
30  
When the Series II Modem 336+ (MD1640A) is  
in dial backup mode, it periodically checks the  
lease line to see if it is operational and tries to  
restore the lease line if possible. S18 defines  
how often attempts occur. The default of S18  
is 30 minutes and can be set in one-minute  
increments from 10 to 255 minutes. Setting the  
S18 restoral under 10 minutes causes excessive  
breaks in dial-up operation.  
97  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S19  
Dial-Back Timer (336+ Only)  
Unit:  
Minutes  
Range:  
0-255  
Default:  
Description:  
1
In the Series II Modem 336+ (MD1640A), S19  
is a timer that begins when the lease line goes  
down. S19 specifies the duration of time the  
modem attempts to reestablish the lease line  
connection.  
S24  
PBX/CBX Disconnect Drop Time for DSR/CTS/CD  
Unit:  
50-mSec intervals  
Range:  
0-255  
Default:  
Description:  
20  
Some PBX and CBX phone systems require the  
modem’s DSR, CTS, and/or CD signal(s) to  
behave in a certain manner when calls are  
disconnected. The Series II Modem’s &R, &S,  
and &C commands cause the modem to drop  
these signal(s) for a specified time period upon  
disconnect, and then bring the signal(s) up  
again. S24 defines the length of time that the  
signals drop. The default setting of 20 results in  
a one-second drop time, which is what most  
PBX/CBX systems with this requirement need.  
S25  
DTR Dropout Time  
Unit:  
100-mSec intervals  
Range:  
0 (50 mSec), 1-255  
Default:  
Description:  
0
S25 defines the amount of time that DTR must  
be dropped before the modem disconnects.  
Typically, a disconnect occurs when DTR is  
dropped for 50 milliseconds or more. This  
98  
 
CHAPTER 6: S-Registers  
dropout time can be increased in 100-mSec  
intervals, up to a maximum of 25.5 seconds  
(S25 set to 255). The default S25 setting of zero  
corresponds to a dropout time of 50 mSec.  
All other possible settings (1 through 255)  
correspond to their multiples of 100 mSec.  
S26  
Failed Password Attempts  
Unit:  
Failed attempts  
Range:  
0-255  
Default:  
Description:  
0
S26 counts the number of times there has been  
a failed password attempt. For example, if you  
entered ATS26? and the message 003 were  
displayed, it would mean that someone has  
failed three times to gain access to your modem  
using its password security system.  
S29  
Local Inactivity Timer  
Unit:  
Minutes  
Range:  
1-255  
Default:  
Description:  
20  
S29 defines the amount of idle time that can  
elapse between AT commands after the SETUP  
password has been entered. If this timer expires,  
the LOGIN and SETUP passwords will have to  
be re-entered. S29 only takes effect when the  
modem has been sent a #DB1 command, which  
secures the modem from local and remote con-  
figuration or dialing (i.e., no AT commands can  
be sent until the LOGIN and SETUP passwords  
have been entered).  
99  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S30  
Inactivity Timer  
Unit:  
Minutes  
Range:  
0-255  
Default:  
Description:  
0
S30 causes the modem to disconnect if no data is  
transmitted or received for a specified time. This  
timer runs during both Reliable and Normal  
error correction connections. The timer restarts  
any time a data character is passed through the  
serial port (either sent or received). If noise on  
the phone line causes an error to be received  
during Normal mode, this also restarts the timer.  
The inactivity timer is disabled by setting S30 to  
zero, which is the factory default setting.  
S32  
Time Elapse for Escape Sequence  
Unit:  
Seconds  
Range:  
0-255  
Default:  
Description:  
20  
S32 sets the time period to validate the escape  
sequence. If the time interval expires before  
the escape sequence is employed (by hitting  
RETURN), the escape sequence is aborted.  
The default time is 20 seconds.  
S34  
Buffer Length of Command Mode...After On-line Escape  
Sequence  
Unit:  
ASCII characters  
Range:  
0-60  
Default:  
Description:  
10  
If the number of characters after AT exceeds the  
S34 buffer length value, the buffer is cleared and  
the escape sequence is aborted.  
100  
 
CHAPTER 6: S-Registers  
S36  
Time Between DTR Inactive and Modem Off-Hook  
Unit:  
Seconds  
Range:  
0-255  
Default:  
Description:  
0
The DTR Busy-out feature uses S-Register S36 to  
set the time between DTR inactive (low) and the  
modem going off-hook. S36 can be set in one-  
second intervals from 0 to 255 seconds. With the  
default setting of S36=0, DTR Busy-Out is  
disabled (i.e., DTR won't Busy-Out).  
S37  
Time Between DTR Active and Modem On-Hook  
Unit:  
Seconds  
Range:  
0-255  
Default:  
Description:  
5
S37 sets the time between DTR being active and  
the modem going on-hook (not busy). S37 will  
only function in conjunction with S36.  
S48  
Program V.34bis Connect Speeds  
Unit:  
N/A  
Range:  
Default:  
Description:  
33, 31, 28, 26, 24, 21,19,16,14,12, 96, or 48  
0
Defines which speed modem connects within  
the scope of Enhanced V.34 mode (e.g., if S48 is  
set to 26, the maximum connect speed will be  
26.4K). This register compensates for line  
conditions that have trouble supporting higher  
Enhanced V.34 speeds (e.g., 33.6K, 31.2K, 28.8K,  
26.4K, 24K...). The modem default is a value of  
0, which indicates a connection attempt of  
33.6K.  
101  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
6.2 Reading and Assigning S-Register Values  
The S command is used to assign a value to, and to read the current  
value of, an S-Register. To read an S-Register value, enter the letter S  
followed by the S-register number and a question mark (?), then hit  
RETURN. For example, entering ATS7? and hitting RETURN displays  
the value of S-Register S7 in a 3-digit decimal form. The number 8  
would appear as 008, the number 30 would appear as 030, and the  
number 255 would appear as 255.  
To assign a value to an S-Register, enter the letter S followed by the  
S-Register number and an equals sign (=), and then a decimal response  
to the message “ENTER THE NEW VALUE IN DECIMAL FORMAT”.  
Convert all ASCII characters to their decimal equivalents before  
entering them. S-Register decimal values range from 0-127 for ASCII  
characters, or 0-255 for numeric values.  
6.2.1 Examples of Assigning Values  
1. Let’s say you wish to have longer pauses caused by the comma in a  
dial command; five seconds instead of two. Entering ATS8=5  
assigns 5 as the value for S-Register S8 (meaning the modem  
pauses five seconds for a comma in a dial command).  
2. In a second example, let’s say that you wish to configure the Series  
II Modem to answer incoming calls after the 30th ring instead of  
after the first ring. To configure S-Register S0 with a value of 30,  
enter ATS0=30 and hit RETURN.  
3. In a third example, let’s say you are calling long distance to  
another country code, and it is taking a long time to connect. The  
S-Register S7 (Abort Timer) setting of 45 seconds, is insufficient.  
The abort timer times out and cancels the call before a connection  
is made. To change the S7 value to 55 seconds, enter Command  
mode, then enter ATS7=55 and hit RETURN. Now, after dialing,  
the modem allows 10 more seconds for a carrier signal before  
aborting the call. The additional 10 seconds should provide  
enough time for international calls.  
102  
 
CHAPTER 6: S-Registers  
6.2.2 Examples of Reading Values  
To verify that you entered the value correctly in the above examples,  
enter ATS8? and hit RETURN in the first example, ATS0? in the  
second, and ATS2? in the third example. You should receive the  
response 005 in the first example, 030 in the second example, and 055  
in the third example.  
When configuring the S-Registers, it is a good practice to include the  
verification read-entry in the same command line as the configuration  
assignment-entry. In the three preceding examples, enter ATS8=5S8?,  
ATS0=30S3?, and ATS7=55S7?.  
6.3 AT Command and S-Register Summary  
The vast majority of installations are similar, with the Series II Modem  
being used to dial up a remote installation where the call is automati-  
cally answered. Your Series II Modem has a default configuration to dial  
another 33,600 bps modem that support error correction, data com-  
pression and flow control. If the answering modem is not compatible,  
the Modem can match protocols, provided the protocols are industry  
standard (i.e., ITU or Bell) and not proprietary.  
The &W command, used in conjunction with specific other AT  
commands and S-Registers, can re-configure the Modem to conform to  
a specific application. The command AT&W0 (or AT&W) causes the  
modem to store its current parameters in its nonvolatile RAM. The  
command also sets the modem upon power up, or when it is reset with  
an ATZ command, the modem reads all of its configuration and S-  
Register parameters from RAM, and not from the factory settings in  
ROM (note that you may recall factory installed defaults by entering  
AT&F8&W0). The &W command changes the configuration para-  
meters stored in RAM that you specifically intend to alter. All other  
default parameters remain unchanged.  
The AT&W1 command sets the modem so that it does not store its  
parameters in RAM, and on power up or when an ATZ command is  
issued, parameters are read from the factory default settings in ROM.  
Before using the &W command, you may want to view the modem's  
current operating parameters. Use the ATL5, ATL6 and ATL7 com-  
mands to display the current modem configuration.  
103  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
7. Callback Security  
and Remote Configuration  
7.1 Introduction  
This chapter describes how the Series II Modem Callback and Remote  
Configuration features operate. These features use a multilevel security  
system, which involves the use of LOGIN Passwords, Setup Passwords  
and Remote Escape Characters.  
The primary level security code is the modem’s LOGIN Password. Once  
this password is entered, other passwords can be used. For instance,  
entering the LOGIN Password will allow you to enter the Setup Pass-  
word, which, in turn, allows you to enter Callback Passwords and dial  
back phone numbers. Callback Passwords tell your modem what dial  
back phone number to call.  
The Remote Escape Character is the key to using the Remote Configu-  
ration feature. The Remote Escape Character lets you enter Command  
mode via a remote call, so that you can enter AT commands just as if  
you were locally connected. You must also enter your modem’s Setup  
Password. The Remote Escape Character is contained in S-Register S13.  
7.2 Callback Feature Description  
The Callback feature protects your network from unauthorized access  
and helps control long distance costs. By use of Callback Passwords and  
dial back phone numbers, you can have your modem "dial back"  
remote locations immediately after being called. A special command  
(Enable Callback #DB) turns your modem into a Callback security  
modem. The Callback Password/Phone number entry is protected  
by two-level security (your modem's LOGIN Password and Set-Up  
Password) that keeps unauthorized personnel from changing parame-  
ters. When you first get your modem, you need to change both security  
level codes to your unique settings.  
The Callback Passwords and dial back phone numbers are in a special  
Callback Password/dial back phone number memory (30 numbers  
104  
 
CHAPTER 7: Callback Security and Remote Configuration  
long). You use the modem's LOGIN Password and the Set-Up Password  
plus special Callback commands to access this memory. The memory is  
thirty numbers long and replaces your modem's normal phone number  
memory.  
Each number is 35 characters long and can contain commands as well  
as phone numbers. You need to set up your modem with the numbers  
and codes as part of the dial back initialization procedures. Your  
modem will also remember if the incoming call was reliable or not,  
and make the call back accordingly.  
7.3 Remote Configuration Description  
The Remote Configuration feature is a network management tool that  
allows you to configure modems remotely. This means you could config-  
ure modems anywhere in your network from one location without  
having to visit the sites or rely on remote users to follow your instruc-  
tions. With Remote Configuration, which is protected by two level  
security, you can download new parameters, program new V.42  
capabilities and implement new features. Remote Configuration also  
makes troubleshooting a remote location a lot easier.  
The way Remote Configuration works is that S-Register S13 has been set  
up to contain the special Remote Configuration escape code. When  
calling a Remote Configuration equipped modem, you enter the  
proper Remote Escape code to enable entering your Set up Password.  
After entering it, you can then execute AT commands as if you were  
connected locally. If you set S-Register S13 to zero, Remote  
Configuration is disabled.  
7.3.1 Initial Setup Procedures for Callback  
and Remote Configuration.  
Your modem was shipped with a default LOGIN Password and Setup  
Password (LOGIN=BLACK BOX and Set-up=MODEMSETUP) so that  
you have access to the features used for configuring the modem.  
Because the defaults are in the modem owner’s manual, and anyone  
can find out what they are, you should change the codes as the first step  
of your initialization procedure.  
105  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Table 7-1. Modem LOGIN, Setup and Remote Escape Code  
Procedures  
To change your modem’s LOGIN Password and Setup Password:  
Step  
Procedure  
Note: Passwords are upper/lower case sensitive. The case you enter  
here is the case that must be used at Log-In.  
1. Type AT#IBLACK BOX and hit RETURN. Your modem will  
respond with:  
OK (if the LOGIN Password is wrong, the modem’s response is  
ERROR)  
2. Type AT#SMODEMSETUP and hit RETURN. Your modem will re-  
spond with the following:  
OK (or ERROR if wrong Setup Password)  
Note: At this point you can change the LOGIN Password and  
Setup Password.  
3. Type AT#I=xxxxxxxxxx (with any keyboard characters used,  
minimum 6 maximum 10) and hit RETURN. Your modem  
responds with:  
OK  
4. Type AT#S=yyyyyyyyyy (with keyboard characters used,  
minimum 6 maximum 10) and hit RETURN. Your modem  
responds with:  
OK  
To change your Remote Configuration feature status:  
5. If you want Remote Configuration off, set S-Register S13 to 0  
(zero). Refer to Chapter 6 for details on how to set S-Register  
values.  
6. If you want Remote Configuration on and wish to change the  
Remote Escape Character, change the S-Register S13 value. If you  
leave it at the default value, decimal 37 (% sign) will be your  
modem’s remote escape character.  
106  
 
CHAPTER 7: Callback Security and Remote Configuration  
To turn your modem's Callback Security feature on and off:  
7. If you want Callback Security with both remote and local password  
security, enter AT#DB1 and hit RETURN. You must turn on  
Callback Security to be able to enter dial back phone numbers.  
8. If you want Callback Security on with just remote password security,  
enter AT#DB2 and hit RETURN. You must turn on Callback  
Security to be able to enter dial back phone numbers. If you want  
to use your modem to call another modem that is also set for  
Callback, you must enter AT#DB3 before you dial.  
Note: This is for your modem if you are set for #DB1 or #DB2.  
Once you have disconnected from that call, your modem will go  
back to its original setting.  
9. If you want Callback Security turned off, type AT#DB0 and hit  
RETURN.  
To set parity of the password/message prompt:  
10. The parity default value for your modem is no parity (AT#P0). If  
your modem's prompt messages use even parity, enter AT#P2 and  
hit RETURN. For odd parity, enter AT#P1 and hit RETURN.  
11. Enter the &W0 command and hit RETURN to store parameters  
and S-Register values in RAM.  
107  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Table 7-2. Callback Password and Dial Back Phone Number Entry  
Procedures  
Step  
Procedure  
1. Enter your modem's LOGIN Password (as selected in Table 7-1)  
by entering the following:  
AT#Ixxxxxxxxxx<CR> (xxxxxxxxxx from Table 7-1)  
Enter your modem's Setup Password (as selected in Table 7-1)  
by entering the following:  
AT#Syyyyyyyyyy<CR>(yyyyyyyyyy from Table 7-1)  
2. Enable the Callback Security feature by entering the following:  
AT#DB2<CR>ÊorÊAT#DB1<CR>  
The following message is displayed on your monitor:  
Entering Callback Mode, current phone numbers will be erased. Do you  
want to continue? (Y/N)  
3. Enter a Y or N and hit RETURN.  
Note: If this is your first time into Callback Mode, we recommend  
answering Y to clear all previous Callback Passwords and phone  
numbers from memory.  
4. Enter individual Callback Passwords for each of 30 different phone  
number memory locations as follows:  
AT#CBN0xxxxxxxxxx<CR>  
To enter Callback Password for the first location (a minimum 6  
characters, up to a maximum of 10 characters must be used).  
AT#CBN1xxxxxxxxxx<CR>  
To enter Callback Password for the second location...etc (a  
minimum 6 characters, up to a maximum of 10 characters must  
be used).  
Note: The first character of your first Callback Password must  
be non-numeric.  
5. Enter individual phone numbers for each of the 30 memory  
locations as follows:  
AT+ - DP...????N0 <CR> (number for location N0)  
108  
 
CHAPTER 7: Callback Security and Remote Configuration  
AT+ - DT...????N1 <CR> (number for location N1)...etc  
Note: You must indicate within the command string that the  
modem either Pulse dials (ATDP...) or Tone dials ATDT...).  
The maximum length of the number is 35 characters. The number  
may include commands as well as your number, so as to create  
macro-type command numbers.  
The + and/or - characters entered before the phone number are  
optional. The + (Deposit Number) code allows a caller to enter the  
number he or she wishes the Callback modem to call back when  
the caller uses a particular password (Step 3 of Table 7-3). The -  
character enables direct entry when the caller uses that correct  
password (Step 3 of Table 7-3) without the Callback modem having  
to return the call.  
The ??? entry at the end of the phone number is optional and indi-  
cates a subcode number to the main phone number for that  
location. The ??? used to dial different extensions at the same basic  
number. To use this optional feature, enter the number of ? marks  
where indicated equal to the number of digits in the desired  
extension number, (i.e., with a 4 digit extension enter ????). When  
a caller uses that particular password (Step 3 of Table 7-3), he or  
she then enters an extension number directly after the password,  
with the same number of digits as the number of ? marks originally  
entered. When calling back that particular number, your modem  
will also dial the indicated extension number.  
Note: To view Callback Passwords/Numbers, use the L Command.  
6. To store changed parameters to memory, enter AT&W0 and hit  
RETURN.  
Note: If you have enabled Callback Security (#DB1 in step 2 of  
Table 7-2), the Series II Modem will be secured locally. To gain  
local access, you must again perform steps 7 and 8.  
7. Enter your modem's LOGIN Password (as selected in Table 7-1)  
by entering:  
AT#Ixxxxxxxxxx<CR> (xxxxxxxxxx from Table 7-1)  
8. Enter your modem's Setup Password (as selected in Table 7-1)  
by entering:  
AT#Syyyyyyyyyy<CR> (yyyyyyyyyy from Table 7-1)  
109  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Table 7-3. Callback Operational Sequence Procedures  
Perform the following steps when dialing into a dialback modem:  
Step  
Procedure  
1. When called, the modem answers and after a slight delay, responds  
with:  
Password>  
2. Enter your modem's LOGIN Password (Table 7-1) and hit  
RETURN. If entered correctly, the modem responds with:  
DB>  
3. Enter the Callback Password corresponding to the phone number  
you wish called back and hit RETURN (Callback Passwords and  
phone numbers entered in Table 7-2). You can also use special  
characters + and -. They must have been entered as part of the  
Callback phone numbers in Step 5 of Table 7-2. If you use the -  
character along with your password, the Callback modem will  
connect directly without hanging-up and calling back. If you use  
the + character along with your password, you can also enter a  
phone number which you wish the Callback modem to dial after  
hanging-up. The + and - characters must be entered after the Dial-  
back password, (i.e., DB>xxxxxx+). This is also the point where  
you enter an extension number if your Callback number used the  
??? feature (Step 5 in Table 7-2).  
You have three tries at each prompt to enter the information  
properly, with an incorrect entry resulting in a password retry. You  
must enter the requested information correctly within one minute  
or the Callback modem will hang-up. When the information is  
entered properly, the called modem will hang-up and after a  
15-second delay, call you back. When your modem answers, the  
dialback modem will respond with the following:  
Password>  
4. Enter the modem's LOGIN Password again (the same as in Step 1).  
The Callback modem responds with:  
CONNECT  
You are now in Data Mode.  
110  
 
CHAPTER 7: Callback Security and Remote Configuration  
7.3.2 Remote Configuration Procedures  
The procedures for using the Remote Configuration features are the  
same whether or not a call originates from the remote modem. Once  
the modem is on-line, perform the procedures in Table 7-4.  
Table 7-4 Remote Configuration Operation Procedures  
Step  
Procedure  
1. Remote Escape Configuration requires %%%AT<CR> to be sent  
if the default value in S-Register S13 has not been changed.  
The modem responds with:  
1. - DATA Mode  
2. - COMMAND Mode  
2. You then select 1 or 2. With 1, the modem goes back into data  
mode and with 2, the modem responds with the following:  
Password>  
3. Enter your Setup Password, and if the code is correct the modem  
responds with:  
OK  
You can now use any AT commands of the modem being remotely  
configured as if they were being entered locally. You cannot change  
the setup of the LOGIN Password until you enter the proper  
LOGIN Password.  
4. When you are done entering AT commands and you want to exit,  
type AT0 and hit RETURN. The modem responds with:  
1. DATA Mode  
2. COMMAND Mode  
5. Enter a 1 to go back on-line with your computer, or enter 2  
and the correct password to talk to your modem.  
111  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
7.4 Remote Configuration and Callback Security  
AT Commands  
The following AT commands are used with Remote Configuration  
and Callback Security features.  
Assign Passwords for Callback Phone Numbers #CBN  
When you have callback security enabled for the Series II Modem,  
anyone trying to connect with the modem will be required to furnish a  
password. The #CBN command allows you to enter passwords for each  
of the 30 memory locations used for callback security. The length of  
each password can be up to 10 characters, but must be at least 6  
characters. Any ASCII character can be used.  
The format for this command is AT#CBNyyxxxxxxxx<CR> with  
xxxxxxxx representing the password and yy being the memory  
location (0-29). Each callback password (xxxxxxxx) must start with  
a non-numeric character.  
Callback Security Enable/Disable #DB  
The purpose of this command is to enable or disable (default setting)  
your modem's callback security option. Once this command is  
executed, you modem will undergo some significant changes. For  
example, the phone number memory locations (N0 through N9) will  
be used for passwords and phone numbers. In other words, you will not  
be able to dial from memory or use the DTR dialing feature.  
You can turn on callback security by typing AT#DB1 or AT#DB2 and  
pressing <CR>. If you want to engage both remote and local password  
security, use the #DB1 command. This sets up the modem so you have  
to provide passwords to dial into the modem and to dial out. For  
remote password security only, use the #DB2 command. This allows the  
local operator to dial out without providing the LOGIN and SETUP  
passwords. Use #DB3 when calling another modem with callback  
security active.  
112  
 
CHAPTER 7: Callback Security and Remote Configuration  
Change LOGIN Password #I  
The default LOGIN password for your Series II Modem is "BLACK  
BOX". If you choose to activate callback security, you should change the  
LOGIN password using this command in the following format:  
AT#Ixxxxxxxxxx<CR> (where xxxxxxxxxx is the current LOGIN  
password)  
Your modem will respond with "OK", indicating that you can enter the  
new LOGIN password as follows:  
AT#I=yyyyyyyyyy<CR>  
You can select any combination of keyboard characters (upper/lower  
case sensitive) between six and ten characters long.  
Change SETUP Password #S  
The default SETUP password for your Series II Modem is  
"MODEMSETUP". If you choose to activate callback security, you should  
change the SETUP password using this command in the following  
format:  
AT#Stttttttttt<CR> (where tttttttttt is the current SETUP password)  
Your modem will respond with "OK", indicating that you can enter the  
new SETUP password as follows:  
AT#S=uuuuuuuuuu<CR>  
You can select any combination of keyboard characters (upper/lower  
case sensitive) between six and ten characters long.  
Erase Callback Password #RCBNxx  
This command erases the single callback password specified by xx  
(0 through 29).  
Erase Callback Phone Number #RDNxx  
This command erases the single phone number specified by xx  
(0 through 29).  
113  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
7.5 Remote Configuration/Callback Security  
S-Registers  
The following S-Registers are used with Remote Configuration and  
Callback Security features.  
Remote Configuration Character (S13)  
S13 defines the Series II Modem remote configuration escape character.  
When the S13 character is entered three consecutive times from a  
remotely connected site, your modem responds to it with its Remote  
Configuration procedure.  
Units:  
Decimal equivalents of ASCII characters  
Range:  
Default:  
0-127  
37 (% sign)  
Callback Time Delay (S15)  
S15 defines the time delay for Callback attempts after initial passwords  
have been exchanged between modems.  
Unit:  
Range:  
Default:  
Seconds  
10-255  
20  
Callback Attempts (S16)  
S16 defines the number of Callback attempts after initial passwords  
have been exchanged between modems.  
Unit:  
Range:  
Default:  
Attempts  
1-255  
4
114  
 
CHAPTER 7: Callback Security and Remote Configuration  
Failed Password Attempts (S26)  
S26 counts the number of times there has been a failed password  
attempt. For example, if you entered ATS26? and the message 003  
were displayed, that would mean someone had failed three times to  
gain access to your modem using its password security system.  
Units:  
Failed attempts  
Range:  
Default:  
0-255  
0
Local Inactivity Timer (S29)  
S29 defines the amount of idle time that can elapse between AT com-  
mands after the SETUP password has been entered. If this timer  
expires, the LOGIN and SETUP passwords will have to be re-entered.  
S29 only takes effect when the modem has been sent a #DB1 command,  
which secures the modem from local and remote configuration or  
dialing (i.e., no AT commands can be sent until the LOGIN and SETUP  
passwords have been entered).  
Units:  
Range:  
Default:  
Minutes  
1-255  
20  
115  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
8. Modem Testing  
8.1 Introduction  
Each time you power up the Series II Modem, it performs an automatic  
self- test to ensure proper operation. The Modem also has four diag-  
nostic test features: Local Analog Loopback, Digital Loopback  
(remote/automatic), Digital Loopback (local/manual) and a  
modem Back-to-Back test.  
A loopback test involves entering data from your PC and looping that  
data through the circuits of your modem and/or a remote modem.  
When the loop has been completed, the original data entered should  
match the data received back on your PCs monitor after the test.  
The Local Analog Loopback Test allows you to verify that the modem’s  
transmitter and receiver circuits are functioning properly.  
The Digital Loopback Test (local/manual) allows you to verify that the  
remote computer or terminal, the remote modem, serial ports, the  
telephone line and the local modem are functioning properly.  
The Digital Loopback Test (remote/automatic) allows you to verify that  
the local computer or terminal, the two modems and the transmission  
line between them are functioning properly.  
The Back-to-Back test lets you connect two Series II Modems with a  
back-to-back cable to verify proper modem operation.  
In asynchronous mode, upon completion of testing, enter either  
Escape Sequence, +++AT<CR> or <BREAK>AT<CR>.  
Note: All loopback tests will operate at all speeds except 300 bps.  
Disable error correction (&E0&W0<CR>) before engaging in  
loopback tests (self-test and back-to-back test not affected).  
116  
 
CHAPTER 8: Modem Testing  
8.2 Local Analog Loopback Test/V.54 Loop 3  
In this test, data from your computer or terminal is sent to your  
modem's transmitter, converted into analog form, looped back to the  
receiver, converted into digital form and then received back at your  
monitor for verification. No connection to the phone line is required.  
See Figure 8-1.  
Computer or Terminal  
Local Series II Modem  
UUUUU  
UUUUU  
analog  
digital  
Type ATU0 or ATU1; hit ENTER  
Figure 8-1. Local Analog Loopback Test  
The test procedure is as follows:  
1. Connect the modem to your computer. With your communication  
software, set the desired baud rate.  
2. Type ATU0 (or ATU) and hit ENTER. This places your modem in  
Analog Loopback mode, in the Originate mode. The modem is  
now out of the Command mode and in a pseudo On-Line mode.  
3. Once you receive a connect message (if responses are enabled),  
enter data from your keyboard. For this test, typing multiple upper  
case "U" characters is a good way to send an alternating test pattern  
of ones and zeros.  
4. For a more complete test, you should also test the modem in  
Answer mode. To do this, you must “escape” from Originate  
mode by entering an Escape Sequence (+++AT<CR> or  
<BREAK>AT<CR>) . Then type ATU1 and hit ENTER to place  
the modem in Analog Loopback mode, in the Answer mode.  
Then repeat step 3.  
117  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
5. When testing is completed, you may exit Answer mode by entering  
an Escape Sequence (+++AT<CR> or <BREAK>AT<CR>), which  
returns the modem to Command mode.  
6. Your modem passes this test if the data entered from your keyboard  
is the same as the data received on your monitor. If different data is  
appearing on your monitor, your modem is probably causing the  
problem, although it could also be your computer. If your modem  
passes this test, but you are receiving errors while On-line, the  
remote modem or the phone line could be at fault.  
8.3 Digital LoopbackTest/V.54 Loop 2 (Local/Manual)  
In this test, your modem must be On-Line with another modem that  
can respond to a request for Digital Loopback, such as another Series II  
Modem. The Digital Loopback Test is an on-line test that loops data  
sent from one modem across the phone line to another modem, then  
back to the first modem. See Figure 8-2.  
There are two ways to put a modem into Digital Loopback mode.  
1. Locally or Manually, described here in section 8.3.  
2. Remotely or Automatically, see section 8.4.  
Note: The Digital Loopback Tests can only be used with the  
modem in Normal mode (error correction off).  
Computer  
or Terminal  
Computer  
or Terminal  
Local Series II  
Modem  
Remote Series II  
Modem  
UUUUU  
UUUUU  
analog  
digital  
analog  
digital  
Type AT in Terminal mode; hit ENTER;  
dial remote modem; establish On-line  
mode; enter escape sequence;  
type ATU3 and hit ENTER  
Figure 8-2. Digital Loopback Test (local/manual)  
118  
 
CHAPTER 8: Modem Testing  
In this test the local modem is placed in Digital Loopback mode. Data  
is entered and transmitted from the remote modem (which is not in  
digital loopback mode), sent across the phone line to the local modem  
and looped back to the remote modem.  
The test procedure is as follows:  
1. Go into Terminal mode. Type AT and hit ENTER; you should get  
an OK message.  
2. Dial the remote modem by entering the Dial command and the  
phone number, to establish On-line mode.  
3. Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>)  
which brings your modem into Command mode, while still main-  
taining the pseudo On-line mode with the remote modem.  
4. Type ATU3 from the local PC and hit ENTER. Once you receive an  
OK message from your modem (if responses are enabled), the local  
modem is placed in Digital Loopback mode.  
5. Data is typed from the remote keyboard. For this test, typing  
multiple upper case "U" characters is a good way to send an alter-  
nating test pattern of ones and zeros. The data received by the local  
modem will enter its analog receiver, be converted to digital data,  
be reconverted into analog, and then looped through its  
transmitter back to the remote modem. Your modem passes this  
test if the data entered from the remote keyboard is the same as  
the data received on the remote monitor.  
6. When testing is complete, you may end the test by typing an Escape  
Sequence (+++AT<CR> or <BREAK>AT<CR>) to bring your  
modem into Command mode. The modem should respond with  
an OK message. If you wish to stay On-line with the remote modem  
for normal data transmission, type AT0 and hit ENTER. If you wish  
to terminate the call, type ATH and hit ENTER to hang up.  
119  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
8.4 Digital Loopback Test/V.54 Loop 2  
(Remote/Automatic)  
In this test, your modem must be On-line with another modem set up  
to respond to a request for Digital Loopback, such as another Series II  
Modem. With the Modem, this ability to respond is controlled by the  
&T command. AT&T4 enables the response to Digital Loopback Test  
(remote/automatic). AT&T5 disables the response. The modem  
defaults to disable on power up, so this must be changed on the remote  
modem before the modem will respond to a request for the Digital  
Loopback Test (remote/automatic).  
Initiate the Digital Loopback Test (remote/automatic) with the ATU2  
command which automatically places the remote modem in digital  
loopback mode. Data from your computer or terminal are transmitted  
through your modem, and over the phone line to the remote modem,  
where they are then looped back to your modem. See Figure 8-3.  
The test procedure is as follows:  
1. Go into Terminal mode. Type AT and hit ENTER; you should get  
an OK message.  
2. Dial the remote modem by entering the Dial command and the  
phone number, to establish On-line mode.  
Note: The &T4 command must be set on the remote modem to  
run this test.  
Computer  
or Terminal  
Computer  
or Terminal  
Local Series II  
Modem  
Remote Series II  
Modem  
UUUUU  
UUUUU  
digital  
analog  
analog  
digital  
Type AT in Terminal mode; hit ENTER;  
dial remote modem; establish On-line  
mode; enter escape sequence; type ATU2  
and hit ENTER  
Figure 8-3. Digital Loopback Test (remote/automatic)  
120  
 
CHAPTER 8: Modem Testing  
3. Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>)  
which brings your modem into Command mode, while still main-  
taining the connection with the remote modem.  
4. Type ATU2 and hit ENTER. The local modem responds to this  
command by transmitting an unscrambled marking signal, which  
causes the remote modem to place itself in Digital Loopback mode.  
Then the local modem exits Command mode and enters pseudo  
On-line mode.  
5. Type data from your keyboard. For this test, typing multiple upper  
case "U" characters is a good way to send an alternating test pattern  
of ones and zeros. The data received by the remote modem will  
enter its analog receiver, be converted to digital data, be reconvert-  
ed into analog, and then looped through its transmitter back to the  
local modem. Your modem passes this test if the data entered from  
the local keyboard is the same as the data received on your  
monitor.  
8.5 Back-to-Back Test  
This test lets you connect two Series II Modems with an RJ11 cable to  
verify proper operation. (See Figure 8-4A on the next page.) Using a  
Series II Modem that is known to be operational, you can test a second  
Modem that is suspect.  
1. Plug the modular ends of an RJ11 cable into both Modems’ LEASE  
jacks (336+ models) or LINE jacks (336 models).  
2. Force DTR ON in both local and remote modems (Switch #1  
DOWN).  
3. Enter the command AT$SB9600$BA0&W0<CR> on both local  
and remote modems. This sets the serial speed to 9600 bps. Make  
sure that the terminal/computer is also set for 9600 bps.  
4. Set both modems in Leased-Line mode (DIP-Switch # 10 DOWN).  
5. Set one Series II Modem to Answer enabled (DIP-Switch #5 UP)  
and the other Modem to Originate enabled (DIP-Switch #5  
DOWN). Note that it does not matter which modem (local/remote)  
is set to Answer/Originate—just so they are set opposite.  
121  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
6. Set DIP-Switch # 3 UP on both local and remote modems. This  
changes the transmit level to -15dB and this change is necessary  
to operate in back-to-back mode  
7. Turn on both units and wait for carrier detect (CD).  
8. Short out pins 2 and 3 on the RS-232C interface on the remote  
modem (with a paper clip or some other metal device, for  
example).  
Remote sites:  
Short Pins 2 and 3  
of the RS-232  
interface  
PHONE  
PSTN  
LEASE  
INTERFACE  
PHONE  
LINE  
INTERFACE  
ON  
ON  
OFF  
OFF  
VOLUME  
POWER  
VOLUME  
POWER  
PHONE  
PSTN  
LEASE  
INTERFACE  
PHONE  
LINE  
INTERFACE  
ON  
ON  
OFF  
OFF  
VOLUME  
POWER  
VOLUME  
POWER  
Figure 8-4A. Back-to-Back Test Cabling  
122  
 
CHAPTER 8: Modem Testing  
9. Entered characters should echo back to the sending modem.  
“Local”  
modem  
Back-to- “Remote”  
back cable modem  
DTE  
Figure 8-4B. Back-to-Back Testing  
8.6 Synchronous Mode Testing  
The following tests must be run with your modem in Synchronous  
mode (DIP Switch #12 in the Up (OPEN) position), DIP Switch #9  
controls the modem’s Synchronous mode testing function. (Refer to  
Chapter 9 for DIP Switch information.) The test procedures for  
Synchronous mode are different from those for Asynchronous mode.  
In Synchronous mode, you cannot access the modem’s AT commands.  
With DIP Switch #9, you can perform either the Digital Loopback Test  
(remote/automatic) or the Digital Loopback Test (local/manual) in  
Synchronous mode, as described in the following sections. There is also  
a Local Analog Loopback Test, documented in section 8.7.  
8.7 Local Analog LoopbackTest (Synchronous Mode)  
This test diagnoses the connection between your Series II Modem and  
your computer or terminal. In Local Analog Loopback Test mode, data  
entered at the local computer or terminal are sent through the local  
modem’s transmit and receive circuits (much like entering an ATU or  
ATU1 command in Asynchronous mode). You then compare the test  
characters (multiple upper case “U” characters in Figure 8-5) on your  
monitor with the characters you typed. If the characters don’t match,  
check your computer’s COM port setting, then verify your  
communication software’s configuration.  
123  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
To initiate the Local Analog Loopback Test, with the modem in  
Synchronous mode:  
1. Enter AT&M1U. This first switches your modem form asynchro-  
nous to synchronous mode, and places it into the Analog Loop-  
back/Originate mode. The modem is now out of the Command  
mode and in the pseudo On-Line mode.  
2. Once you receive a connect message (if responses are enabled), enter  
data from your keyboard. For this test, typing multiple upper case  
"U" characters is a good way to send an alternating test pattern of  
ones and zeros.  
3. For a more complete test, you should also test the modem in  
Answer mode. To do this, Type the Escape Sequence (+++AT<CR>  
or <BREAK>AT<CR>) which brings your modem into Command  
mode, while still maintaining the connection. Then type  
AT&M1U1 and hit ENTER to place the modem in Analog  
Loopback mode, in the Answer mode. Then repeat step 2.  
Local Series II Modem  
Computer or  
Terminal  
UUUUU  
UUUUU  
analog  
digital  
Type ATU0 or ATU1; hit ENTER  
Figure 8-5. Synchronous Mode Local Analog Loopback Test  
8.8 Digital Loopback Test (Local/Manual)  
(Synchronous Mode)  
This test must be run when you have a data connection with another  
modem. If a Local Analog Loopback Test resulted in errors, and this  
test passes without errors, then the problem exists in your computer-to-  
modem connection. In Digital Loopback Test (local/manual) mode,  
124  
 
CHAPTER 8: Modem Testing  
data passed from the remote modem’s transmit circuit are looped back  
from the local modem and are received at the remote modem’s receive  
circuit (multiple upper case “U” characters in Figure 8-6).  
First make certain that you are set up for Synchronous operation by  
placing DIP-Switch #12 in the UP position. To initiate the Digital  
Loopback Test (local/manual), DIP-Switch #9 must be in the UP  
position, and the Answer/Originate switch (front of the modem) must  
be toggled to the UP position. Once you receive an OK message from  
your modem (if responses are enabled), the local modem is placed in  
Digital Loopback mode.  
To exit the Digital Loopback Test (local/manual), toggle the  
Answ/Orig switch to the Answer position.  
Computer  
Computer  
or Terminal  
or Terminal  
Local Series II  
Modem  
Remote Series II  
Modem  
UUUUU  
UUUUU  
digital  
analog  
analog  
digital  
DIP switch #9  
UP; Answ/Orig  
switch toggled to  
Answ position  
when On-line  
Figure 8-6. Synchronous Mode Digital Loopback Test  
(local/manual)  
8.9 Digital Loopback Test (Remote/Automatic)  
(Synchronous Mode)  
This test must be run when you have a data connection with another  
modem. In this test, data is passed to the remote modem and is looped  
back to the local modem (as if an ATU2 command was issued in  
Asynchronous test mode), as shown in Figure 8-7. This lets you test the  
local and remote modem’s transmit and receive circuits, as well as your  
computer’s serial COM port and the phone lines. If the test results in a  
mismatch of entered/received data (multiple upper case “U” characters  
125  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
in Figure 8-6), the Local Analog Loopback Test should be performed  
on both the remote and local modems. If that test is successful, the  
problem may be the phone lines.  
First make certain that you are set up for Synchronous operation by  
placing DIP-Switch #12 in the UP position. To initiate the Digital  
Loopback Test (remote/automatic), DIP-Switch #9 must be in the  
DOWN position, and the Answer/Originate switch (front of the  
modem) must be toggled to the UP position. Once you receive an OK  
message from your modem (if responses are enabled), the local modem  
is placed in Digital Loopback mode. To exit the Digital Loopback Test  
(remote/automatic), toggle the front panel Answ/Orig switch to the  
Answer position.  
Computer or  
Computer or  
Terminal  
Terminal  
Local Series  
II Modem  
Local Series  
II Modem  
UUUUU  
UUUUU  
analog  
digital  
analog  
digital  
Type ATU0 or ATU1; hit ENTER  
Figure 8-7. Synchronous Mode Digital Loopback Test  
(remote/automatic)  
126  
 
CHAPTER 9: DIP-Switch Settings  
9. DIP-Switch Settings  
9.1 Introduction  
There are several DIP-Switch options on the Series II Modem’s printed  
circuit (PC) board. The DIP-Switches are accessible through a cut-out  
on the side of the modem. This chapter explains the Modem printed-  
circuit board options. Sixteen DIP-Switch settings and the modem's  
speaker volume control are explained in detail, including all default  
settings.  
Power switch  
Power jack  
FRONT  
Speaker  
RS/232/V.24  
connector  
LEDs  
Volume knob  
Line jack  
16-position DIP switch  
Phone jack  
OPEN  
OPEN  
Voice/Data  
switch with  
Answ/Orig  
REAR  
1
2
3
4
5
6
7
8
9
10 11 12  
13 14 15 16  
Figure 9-1. Series II Modem 336 (MD1641A) PC Board  
127  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
FRONT  
Power switch  
Power jack  
Speaker  
RS/232/V.24  
connector  
LEDs  
Volume knob  
Leased-ine jack  
Dialup jack  
Phone jack  
REAR  
16-position DIP switch  
OPEN  
OPEN  
Voice/Data  
switch with  
Answ/Orig  
1
2
3
4
5
6
7
8
9
10 11 12  
13 14 15 16  
Figure 9-2. Series II Modem 336+ (MD1640A) PC Board  
9.2 DIP-Switch Option Settings  
Switch #1  
Forced DTR -- "DTR"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The Series II Modem must have a high DTR signal in order to operate.  
DTR is provided to the modem by the terminal or computer to which it  
is attached, through pin 20 of the RS-232C/V.24 interface. If your  
terminal or computer is not providing DTR to the modem, you can  
force the DTR signal high with DIP-Switch #1.  
DTR function normally  
DTR forced On  
Factory Default Setting  
=
=
=
Switch #1 UP  
Switch #1 DOWN  
UP  
128  
 
CHAPTER 9: DIP-Switch Settings  
Switch #2  
Flow Control - &E4/&E5  
(Asynchronous Mode/Leased Line/Dial-Up)  
With Hardware Flow Control, the modem uses its RS-232C/V.24  
interface to control the flow of data from the computer or terminal to  
which it is attached. The CTS signal on Pin 5 of the RS-232C/V.24 is  
brought low to stop the flow of data, and is brought high to restart it.  
Place DIP-Switch #2 in the UP position to enable Hardware Flow  
Control (&E4). Xon/Xoff Flow Control (&E5) is another flow control  
method. Xon/Xoff characters in the data dictate the start and stop of  
data flow from the computer or terminal. Place DIP-Switch #2 in the  
DOWN position to select Xon/Xoff Flow Control.  
Hardware Flow Control (&E4)  
Xon/Xoff Flow Control (&E5)  
Factory Default Setting  
=
=
=
Switch #2 UP  
Switch #2 DOWN  
UP  
Switch #2  
SDLC/BSC Option  
(Synchronous Mode/Leased Line/Dial-Up)  
Synchronous Data Link Control (SDLC) and Binary Synchronous  
Control (BSC) are two error correction protocols used in the IBM  
Mainframe environment. Place DIP-Switch #2 in the UP position to  
enable SDLC mode, and place DIP-Switch #2 in the DOWN position to  
enable BSC mode.  
SDLC Mode  
BSC Mode  
Factory Default Setting  
=
=
=
Switch #2 UP  
Switch #2 DOWN  
UP  
129  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Switch #3  
Enable/Suppress Responses -- "Q"  
(Asynchronous Mode/Dial-Up)  
In some Asynchronous mode applications, you may want to suppress all  
responses from the modem. Place DIP-Switch #3 in the DOWN position  
to enable Result Code responses (Q0). Place DIP-Switch #3 in the UP  
position, and answer mode is handled without responses and echo  
turned off (Q2), but originate is still intelligent.  
Enable Responses: Originate/Answer (Q0)  
Suppress Responses: Answer (Q2)  
Factory Default Setting  
=
=
=
Switch #3 DOWN  
Switch #3 UP  
DOWN  
Switch #3  
dB Transmission Levels  
(Asynchronous/Synchronous Mode/Leased Line)  
DIP-Switch #3 adjusts dB transmission levels required by some phone  
carriers. Place DIP-Switch #3 in the DOWN position to enable -9 dB  
transmission. Place DIP-Switch #3 in the UP position to enable -15 dB  
transmission.  
-9dB Transmission  
-15dB Transmission  
Factory Default Setting  
=
=
=
Switch #3 DOWN  
Switch #3 UP  
DOWN  
Switch #4  
AS/400 Mode  
(Synchronous Mode/Leased Line/Dial-Up)  
The Series II Modem can function in the IBM AS/400 environment  
(appearing like an IBM 5853 modem). First, DIP-Switch #7 must be  
placed in the UP position. This establishes an RTS/CTS condition  
(state typical for an IBM 5853 modem in half-duplex mode). Next,  
place DIP-Switch #4 in the DOWN position. This "spoofs" the Modem  
into operating like an IBM 5853 modem in AS/400 applications. DIP-  
Switch #4 in the UP position disables this function. Note that the  
Modem must be in Command mode to allow AS/400 mode (DIP-Switch  
#8 DOWN); and in Synchronous mode (DIP-Switch #12 UP).  
130  
 
CHAPTER 9: DIP-Switch Settings  
AS/400 Mode Enabled  
AS/400 Mode Disabled  
Factory Default Setting  
=
=
=
Switch #4 DOWN  
Switch #4 UP  
UP  
Switch #4  
Unix UUCP Spoofing  
(Asynchronous Mode/Leased Line/Dial-Up)  
The Series II Modem can be configured for use with Unix equipment  
which employs ACK flow control to monitor data integrity. The Modem  
can do "UUCP spoofing", where the modem is able to generate ACKs at  
the DTE interface. Data then is transmitted more time-efficiently,  
because the delay of waiting for data to be received then waiting for the  
ACK to be returned at the remote end, is eliminated. Placing DIP-  
Switch #4 in the DOWN position enables UUCP spoofing.  
UUCP Spoofing Enabled = Switch #4 DOWN  
UUCP Spoofing Disabled = Switch #4 UP  
Factory Default Setting  
=
UP  
Switch #5  
Enable/Disable Auto-Answer - "Ans"  
(Asynchronous Mode/Synchronous Mode/Dial-Up)  
In some originate-only applications, you may wish to disable the Series  
II Modem's automatic answering capabilities. This may be true if you  
have a telephone set attached to a modem and wish to receive voice  
calls that you yourself would answer instead of the modem. Place DIP-  
Switch #5 in the UP position to enable Auto-Answer. Place DIP-Switch  
#5 in the DOWN position to disable Auto-Answer.  
Auto-Answer Enabled  
Auto-Answer Disabled  
Factory Default Setting  
=
=
=
Switch #5 UP  
Switch #5 DOWN  
UP  
Switch #5  
Originate/Answer Mode  
(Asynchronous/Synchronous Mode/Leased Line)  
The Series II Modem functions in either Originate mode or Answer  
mode. Place DIP-Switch #5 in the DOWN position to enable Originate  
mode. Place DIP-Switch #5 in the UP position to enable Answer mode.  
131  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Originate Mode Enabled = Switch #5 DOWN  
Answer Mode Enabled  
Factory Default Setting  
=
=
Switch #5 UP  
UP)  
Switch #6  
Maximum Throughput Setting  
(Asynchronous Mode/Leased Line/Dial-Up)  
Some applications require you to dial into services with maximum  
throughput on, and other applications where maximum throughput  
must be off (i.e., service not supporting error correction, or the V.42  
handshake interferes with logon sequence). DIP-Switch #6 is used for  
switching between these two modes. This DIP-Switch controls three  
important parameters (error correction, speed conversion and serial  
port speed), which in effect enables or disables maximum throughput.  
Maximum Throughput Enabled = Switch #6 UP  
Maximum Throughput Disabled = Switch #6 DOWN  
Factory Default Setting  
=
UP  
Switch #6  
Slave Clocking  
(Synchronous Mode/Leased Line/Dial-Up)  
In Synchronous mode, DIP-Switch #6 controls the option of having  
timing controlled by the receive clock. The originate modem, in effect,  
adjusts to the answer (remote) modem. Place DIP-Switch #6 in the  
DOWN position to enable Slave Clocking. Place DIP-Switch #6 in the  
UP position to disable Slave Clocking.  
Slave Clocking Enabled  
Slave Clocking Disabled  
Factory Default Setting  
=
=
=
Switch #6 DOWN  
Switch #6 UP  
UP  
Switch #7  
Request To Send Forced - "RTS"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
If your computer or terminal uses RTS-CTS protocol (typically used in  
some synchronous applications, but also if using hardware pacing for  
V.42 error correction or speed conversion), you may want to set RTS to  
function independently of CTS (DIP-Switch #7 UP). For most  
132  
 
CHAPTER 9: DIP-Switch Settings  
applications, especially asynchronous, this switch should be set so that  
RTS is forced On (DIP-Switch #7 DOWN)  
RTS functions Normally  
RTS forced On  
Factory Default Setting  
=
=
=
Switch #7 UP  
Switch #7 DOWN  
DOWN  
Switch #8  
Enable/Disable Command Mode -- "Com"  
(Asynchronous/Synchronous Mode/Leased/Dial-Up)  
In some applications you may want to disable the Series II Modem's  
Command mode so that the modem does not recognize or react to AT  
or V.25bis commands. This may be true in strictly auto-answer  
applications where no call origination is required. Place DIP-Switch #8  
in the DOWN position to enable Command mode. Place DIP-Switch #8  
in the UP position to disable Command mode. The factory default  
setting is Command mode enabled.  
Disable Command Mode  
Enable Command Mode  
Factory Default Setting  
=
=
=
Switch #8 UP  
Switch #8 DOWN  
DOWN  
Switch #9  
Digital Loopback Test  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
When in Synchronous mode, this switch controls both Local Digital  
Loop and Remote Digital Loop tests while on-line. When the  
Voice/Data switch is toggled to the Answer mode position (UP) and  
DIP-Switch #9 is in the UP position, the Series II Modem performs the  
Local Digital Loopback test. When DIP-Switch #9 is DOWN and the  
Voice/Data switch is toggled to Answer mode position (UP), the  
Series II Modem performs the Remote Digital Loopback test.  
Local Digital Loopback Test  
Remote Digital Loopback Test  
Factory Default Setting  
=
=
=
Switch #9 UP  
Switch #9 DOWN  
DOWN  
133  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Switch #10  
Leased Line/Dial-Up Operation -- "DDD"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The Series II Modem operates in either leased-line or dial-up modes.  
This switch controls leased-line/dial-up operation. Place DIP-Switch #10  
in the UP position for Dial-Up operation. Place DIP-Switch #10 in the  
DOWN position for Leased-Line operation  
Dial-Up Operation  
Leased Line Operation  
Factory Default Setting  
=
=
=
Switch #10 UP  
Switch #10 DOWN  
UP  
Switch #11  
"AT" Responses/Series II Responses  
(Asynchronous Mode/Leased line/Dial-Up)  
In Asynchronous mode, you can set the Series II Modem to respond  
with Result Codes according to the “Series II" command response set  
(Switch #11 in the DOWN position), or to “AT" command response set  
(Switch #11 in the UP position). The &Q command performs the same  
function (choosing AT or Series II Result Codes), and is explained  
further in section 5.3 of this manual.  
“AT" Responses (&Q1)  
“Series II" Responses (&Q0)  
Factory Default Setting  
=
=
=
Switch #11 UP  
Switch #11 DOWN  
DOWN  
Switch #11  
Internal/External Clocking  
(Synchronous Mode/Leased Line/Dial-Up)  
In Synchronous mode, the transmit clock can be supplied by the DTE  
on pin 24 of the RS-232C/V.24 interface by placing DIP-Switch #11 UP.  
Place DIP-Switch #11 in the DOWN position to enable DCE to control  
clocking (internal clock via pins 15 and 17 of the RS-232/V.24  
interface).  
External Clock (pin 24)  
Internal Clock (pins 15/17)  
Factory Default Setting  
=
Switch #11 UP  
=
Switch #11 DOWN  
=
DOWN  
134  
 
CHAPTER 9: DIP-Switch Settings  
Switch #12  
Asynchronous/Synchronous Operation -- "Sync"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The Series II Modem can operate in either Asynchronous mode or  
Synchronous mode. In Synchronous mode, start and stop bits are  
eliminated. The modem's internal clock circuits on the RS-232C/V.24  
pins 15 and 17 are activated. The Series II Modem's Command mode is  
not accessible in Synchronous mode. This switch is a means to alternate  
and to access either mode. In Synchronous mode, you may want to set  
the RTS forcing and CTS forcing DIP-Switches so that both of signals  
act normally (not forced on).  
Synchronous Operation  
Asynchronous Operation  
Factory Default Setting  
=
=
=
Switch #12 UP  
Switch #12 DOWN  
DOWN  
Switches #13 and #14  
Speed Switches  
(Synchronous Mode/Leased Line)  
DIP-Switches #13 and #14 are used to set the Series II Modem’s data  
transmission rate. Switches #13 and #14 are used in combination,  
typically in leased-line and call origination applications. Note that the  
modem baud rate command ($MB33600) overrides the setting of these  
speed selection switches (DIP switches #13 and #14).  
28800 bps Operation  
19200 bps Operation  
14400 bps Operation  
9600 bps Operation  
Factory Default Setting  
=
=
=
=
=
Switch #13 UP and Switch #14 UP  
Switch #13 DN and Switch #14 UP  
Switch #13 UP and Switch #14 DN  
Switch #13 DN and Switch #14 DN  
Switch #13 UP and Switch #14 UP  
Switch #15  
Carrier Detect/DSR Forcing -- "DSR"  
(Asynchronous/Synchronous Mode/Dial-Up/Leased Line)  
Some terminals react in unusual ways to the toggling of the Carrier  
Detect (CD - RS-232C/V.24 pin 6) signals. The most common symptom  
is that the modem does not respond to commands, or does not echo  
characters. In these cases, it is advisable to force these two signals On in  
order for the terminal to communicate properly with the modem in  
135  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Command mode. This is done by setting DIP-Switch #15 DOWN. With  
DIP-Switch #15 in the UP position, both CD and DSR will be either on  
or off, depending on the On-Line status.  
CD and DSR normal  
CD and DSR forced On  
Factory Default Setting  
=
=
=
Switch #15 UP  
Switch #15 DOWN  
UP  
Switch #16  
2 Wire/4 Wire Operation  
(Asynchronous/Synchronous Mode)  
The Series II Modem works over either 2-wire or 4-wire leased lines. To  
select 4-wire operation, place Switch #16 DOWN (Default); and to select  
2-wire operation, place Switch #16 UP.  
2-Wire Leased Line  
4-Wire Leased Line  
Factory Default Setting  
=
=
=
Switch #16 UP  
Switch #16 DOWN  
DOWN  
9.3 Speaker Volume Control  
You can adjust the volume of the Series II Modem’s phone-line monitor  
speaker with a volume control knob, located on the back of the modem  
next to the RS232C connector (see Figure 9-1 for location). Turn the  
knob clockwise to increase the modem's volume and counterclockwise  
to decrease speaker volume. See Speaker Control Command (M) in  
Section 5.4.6.  
136  
 
CHAPTER 9: DIP-Switch Settings  
9.4 Recording Option Configurations  
This section lets you record any changes you may have made to the DIP-  
Switch settings. Circle the appropriate setting and record the effect for  
future reference.  
DIP-Switches  
Sw.  
Function  
PositionEffect  
#1 Force DTR/DTR from Interface* UP*  
DOWN  
UP*  
#2 Flow Control &E4*/&E5  
(Async/Dial-Up/Leased Line)  
DOWN  
#2 SDLC*/BSC (Sync)  
UP*  
DOWN  
#3 Result Codes Enable*/Disable  
(Async/Dial-up)  
UP  
DOWN*  
#3 DbM Transmit -9dB*/-15dB  
(Async/Sync/Lease-Line)  
UP  
DOWN*  
#4 UUCP Enable/Disable*  
(Async/Dial-Up/Leased Line)  
UP*  
DOWN  
#4 AS/400 Enable/Disable*  
(Sync/Dial-Up/Leased line)  
UP*  
DOWN  
#5 Auto-Answer Enable*/Disable  
(Async/Sync/Dial-Up)  
UP*  
DOWN  
#5 Answer*/Originate  
(Async/Sync/Leased Line)  
DOWN  
UP*  
#6 Max-Thru Enable*/Disable  
(Async/Dial-Up/Leased)  
UP*  
DOWN  
#6 Slave Clock Enable/Disable*  
(Sync/Dial-Up/Leased)  
UP*  
DOWN  
#7 RTS/Normal/Forced*  
(Sync/Async/Dial/Leased)  
* Factory Default Setting  
UP  
DOWN*  
137  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Sw. Function  
Position Effect  
#8 Command Mode Enabled*  
(Sync/Async/Dial/Leased)  
UP  
DOWN*  
#9 Local/Remote* LoopBack  
(Async/Sync/Dial/Leased)  
UP  
DOWN*  
#10 Dial-Up*/Leased-Line  
UP*  
DOWN  
#11 “AT" vs. “Series II" Result Codes*  
UP  
(Asynchronous)  
DOWN*  
#11 Internal*/External Clocking  
(Synchronous)  
UP  
DOWN*  
#12 Sync/Async Mode*  
UP  
DOWN*  
* Factory Default Setting  
DIP Switches #13-16  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
CONDITION  
UP/UP*  
EFFECT  
28.8 K bps Operation  
19.2 K bps Operation  
14.4 K bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 9600 bps Operation  
Note: Modem baud rate commands such as $MB33600 override the  
setting of these speed selection switches (DIP switches #13 and #14).  
#15  
#15  
#16  
#16  
UP*  
CD/DSR from Interface  
CD/DSR Forced On  
2-Wire Leased Line  
4-Wire Leased Line  
DOWN  
UP  
DOWN*  
*Standard Factory Default Setting  
138  
 
APPENDIX A: Troubleshooting  
Appendixes  
Appendix A - Troubleshooting  
Your Series II Modem was thoroughly tested at the factory before it was  
shipped. If you are unable to make a successful connection or if you  
experience data loss or garbled characters during your connection, it is  
possible that the modem is defective. However, it is more likely that the  
source of your problem lies elsewhere. Problems you may encounter  
include the following:  
None of the LEDs light when the modem is on.  
The modem does not respond to commands.  
The modem dials but is unable to make a connection.  
The modem disconnects while on-line.  
The modem cannot connect when answering.  
File transfer is slower than it should be.  
I am losing data.  
I am getting garbage characters on the monitor.  
I can’t run my fax and communications software at the same time.  
If you experience problems, please check the possibilities in Section A.1  
before calling Tech Support (see Section A.2).  
A.1 Possible Causes and Solutions  
None of the LEDs Light When the Modem Is On  
When you turn on the Series II Modem, the LED indicators on the  
front panel should flash briefly as the modem runs a self-test. If the  
LEDs remain off, the modem is probably not receiving power.  
Make sure the modem’s power switch is on, especially if you nor-  
mally turn on the modem by turning on a power strip.  
If the power supply is plugged into a power strip, make sure the  
power strip is plugged in and its power switch is on.  
Make sure the power supply module is firmly connected to the  
modem and to the wall outlet or power strip.  
139  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
If the power strip is on and the modem switch is on, try moving the  
modem power supply to another outlet on the power strip.  
Test that the outlet is live by plugging a lamp into it.  
The modem or power supply may be defective. If you have another  
Series II Modem, try swapping modems. If the problem goes away,  
the first modem or power supply may be defective. Call Tech  
Support for assistance.  
CAUTION: Do not under any circumstances replace the power supply  
module with one designed for another product, as it may damage the  
modem and void your warranty.  
The Modem Does Not Respond to Commands  
Make sure the modem is plugged in and turned on. (See “None of  
the LEDs Light When the Modem Is On.”)  
Make sure you are issuing the modem commands from the data  
communications software, either manually in terminal mode or au-  
tomatically by configuring the software. (You cannot send com-  
mands to the modem from the DOS prompt.)  
Make sure you are in terminal mode in your data communications  
program, then type AT and press ENTER. If you get an OK re-  
sponse, your connections are good and the problem likely is in  
your phone book entry or session settings.  
Try resetting your modem by turning it off and on. Make sure there  
is a reset command (&F) in your initialization string, or your  
modem may not initialize correctly.  
If you don’t get an OK, the problem may still be in the communica-  
tions software. Make sure you have done whatever is necessary in  
your software to make a port connection. Not all communications  
programs connect to the COM port automatically. Some connect  
when the software loads and remain connected until the program  
terminates. Others can disconnect without exiting the program  
(make sure the Connect icon looks plugged in). If the terminal  
reports that it cannot make a connection, yet the modem’s TR indi-  
cator is on, click on the Window menu to see if more than one ter-  
minal is open. The modem’s TR indicator shows that the software  
has made a connection with the modem through the COM port.  
140  
 
APPENDIX A: Troubleshooting  
Your communications software settings may not match the physical  
port the modem is connected to. The serial cable may be plugged  
into the wrong connector—check your computer documentation  
to make sure. Or you may have selected a COM port in your  
software other than the one the modem is physically connected  
to—compare the settings in your software to the physical  
connection.  
If the modem is on, the cable is plugged into the correct port, the  
communications software is configured correctly, and you still  
don’t get an OK, the fault may be in the serial cable. Make sure it is  
firmly connected at both ends.  
Is this the first time you have used the cable? If so, it may not be  
correct. Check the cable description on the packaging to make  
sure the cable is the right one for your computer.  
Peripheral expansion cards, such as bus mouse and sound cards,  
may include a serial port pre-configured as COM1 or COM2. The  
extra serial port, or the card itself, may use the same COM port,  
memory address, or interrupt request (IRQ) as your communica-  
tions port. Be sure to disable any unused ports.  
To look for address or IRQ conflicts if you use Windows 3.1x, select  
File, Run in Program Manager, type MSD, and press ENTER. Then  
select Mouse, COM Ports, and IRQ Status and note the addresses  
and IRQs that are in use. If you find an IRQ conflict, note which  
IRQs are not being used, then change one of the conflicting  
devices to use one of the unused IRQs. If you find an address  
conflict, change the address of one of the conflicting devices.  
To change a port address or IRQ in Windows 3.1x, double-click the  
Control Panel icon, then the Ports icon. Click on the port you want  
to change, click Settings, click Advanced, and select the new port  
address and/or interrupt. If you wish to use COM3 or COM4, note  
that COM3 shares an IRQ with COM1, as does COM4 with COM2,  
so you should change their IRQs to unused ones, if possible.  
If you use Windows 95, right-click on My Computer, select Proper-  
ties from the menu, click on the Device Manager tab, double-click  
on Ports, then double-click on the Communications Port your  
modem is connected to. In the port’s Properties sheet, click on the  
Resources tab to see the port’s Input/Output range and Interrupt  
Request. If another device is using the same address range or IRQ,  
141  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
it will appear in the Conflicting Device List. Uncheck Use  
Automatic Settings to change the port’s settings so they do not  
conflict with the other device, or select the port the conflicting  
device is on and change it instead. If you need to open your  
computer to change switches or jumpers on the conflicting device;  
refer to the device’s documentation.  
The serial port may be defective. If you have another serial port,  
install the modem on it, change the COM port setting in your soft-  
ware, and try again.  
The modem may be defective. If you have another Series II  
Modem, try swapping modems. If the problem goes away, the first  
modem is possibly defective. Call Tech Support for assistance (see  
Section A.2).  
The Modem Dials But Cannot Make a Connection  
There can be several reasons the Series II Modem fails to make a con-  
nection. Possibilities include  
lack of a physical connection to the telephone line.  
a wrong dial tone.  
a busy signal.  
a wrong number.  
no modem at the other end.  
a faulty modem, computer, or software at the other end.  
incompatibility between modems.  
You can narrow the list of possibilities by using extended result codes.  
To enable them, enter ATV1X4 and press ENTER while in terminal  
mode, or include V1X4 in the modem’s initialization string. When you  
dial again, the modem will report the call’s progress.  
If the modem reports NO DIALTONE, check that the modem’s  
telephone line cable is connected to both the modem’s LINE jack  
(not the PHONE jack) and the telephone wall jack. If the cable  
looks secure, try replacing it. If that doesn’t work, the problem may  
be in your building’s telephone installation. To test the building  
installation, plug a telephone into your modem’s telephone wall  
jack and listen for a dial tone. If you hear a dial tone, your modem  
may be installed behind a company phone system (PBX) with an  
142  
 
APPENDIX A: Troubleshooting  
internal dial tone that sounds different from the normal dial tone.  
In that case, the modem may not recognize the dial tone and may  
treat it as an error. Check your PBX manual to see if you can  
change the internal dial tone; if you can’t, change your modem’s  
initialization string to replace X4 with X3, which will cause the  
modem to ignore dial tones.  
If the modem reports BUSY, the other number may be busy, in  
which case you should try again later, or it may indicate that you  
have failed to add a 9, prefix to the phone number if you must dial  
9 for an outside line.  
If you must dial 9 to get an outside line, the easiest way to dial it au-  
tomatically is to include it in the modem’s dial prefix, e.g., ATDT9,.  
Note the comma, which inserts a pause before the number is  
dialed. By inserting 9, into the dial prefix, you do not have to in-  
clude it in each directory entry in the terminal.  
To change the dial prefix in Windows Terminal, select Settings,  
Modem Commands. To change it in Windows 95 HyperTerminal,  
select Call, Connect from the menu bar, click Dialing Properties,  
and type 9 in the local and long distance boxes in How I Dial from  
This Location.  
If the modem reports NO ANSWER, the other system has failed to  
go off-hook, or you might have dialed a wrong number. Check the  
number.  
If the modem reports NO CARRIER, the phone was answered at the  
other end, but no connection was made. You might have dialed a  
wrong number, and a person answered instead of a computer, or  
you might have dialed the correct number but the other computer  
or software was turned off or faulty. Check the number and try  
again, or try calling another system to make sure your modem is  
working. Also, try calling the number on your telephone. If you  
hear harsh sounds, then another modem is answering the call, and  
the modems may be having problems negotiating because of  
modem incompatibilities or line noise. Try connecting at a lower  
speed.  
143  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
The Modem Disconnects While On-line  
If you have call waiting on the same phone line as your modem, it  
may interrupt your connection when someone tries to call you. If  
you have call waiting, disable it before each call. In most telephone  
areas, you can disable call waiting by preceding the telephone num-  
ber with *70 (check with your local telephone company).  
You can automatically disable call waiting by including the  
disabling code in the modem’s dial prefix (e.g., ATDT*70,—note  
the comma, which inserts a pause before the number is dialed). To  
change the dial prefix in Windows Terminal, select Settings,  
Modem Commands. To change it in Windows 95 HyperTerminal,  
select Call, Connect from the menu bar, click Dialing Properties,  
check this location has Call Waiting, and select the correct code for  
your phone service.  
If you have extension phones on the same line as your modem, you  
or someone else can interrupt the connection by picking up anoth-  
er phone. If this is a frequent problem, disconnect the extension  
phones before using the modem, or install another phone line es-  
pecially for the modem.  
Check for loose connections between the modem and the  
computer, the telephone jack, and AC power.  
You may have had a poor connection because of line conditions or  
the problem may have originated on the other end of the line. Try  
again.  
If you were on-line with a BBS, it may have hung up on you because  
of lack of activity on your part or because you exceeded your time  
limit for the day. Try again.  
The Modem Cannot Connect When Answering  
Auto-answer may be disabled. Turn on auto-answer in your data-  
comm program or send the command ATS0=1 to your modem  
in terminal mode.  
144  
 
APPENDIX A: Troubleshooting  
File Transfer Is Slower Than It Should Be  
You may have an older UART. For best throughput, install a  
16550AFN UART. See the “Quick Start” chapter for information on  
how to identify your UART.  
If you are running under Windows 3.1 and have a 16550AFN  
UART, you must replace the Windows serial driver, COMM.DRV, to  
take full advantage of the UART’s speed.  
If you are using a slow transfer protocol, such as Xmodem or Ker-  
mit, try Zmodem or Ymodem/G instead.  
Is your line noisy? If there is static on your line, the modem has to  
re-send many blocks of data to insure accuracy. You must have a  
clean line for maximum speed.  
Are you downloading a compressed file with MNP 5 hardware com-  
pression enabled? Since hardware data compression cannot com-  
press a file already compressed by an archiving program, the  
transfer can be marginally slower with data compression enabled  
than with it disabled.  
Try entering the L8 (List Online Diagnostics) command in on-line  
mode, making a screen print of the diagnostics listing, and  
checking for parameters that may be unacceptable (number of re-  
trains, round trip delay, etc.).  
I Am Losing Data  
If you are using data compression and a high speed serial port, set  
the serial port baud rate to four times the data rate.  
Your UART may not be reliable at serial port speeds over 9600 bps  
or 19,200 bps. Turn off data compression, reset your serial port  
speed to a lower rate, or replace your serial port with a faster one.  
Make sure the flow control method you selected in software match-  
es the method selected in the modem. If you have a Macintosh, you  
may have the wrong cable for hardware flow control.  
If you are running under Windows 3.1 and have a 16550AFN  
UART, you may need to turn on the 16550’s data buffers and/or  
replace the Windows serial driver, COMM.DRV.  
145  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Try entering the L8 (List Online Diagnostics) command in on-line  
mode, making a screen print of the diagnostics listing, and  
checking for parameters that may be unacceptable (number of re-  
trains, round trip delay, etc.).  
I Am Getting Garbage Characters on the Monitor  
Your computer and the remote computer may be set to different  
word lengths, stop bits, or parities. If you have connected at 8-N-1,  
try changing to 7-E-1, or vice-versa, using your communications  
software.  
You may be experiencing line noise. Enable error correction, if it is  
disabled, or hang up and call again; you may get a better connec-  
tion.  
At speeds above 2400 bps, the remote modem might not use the  
same transmission or error correction standards as your modem.  
Try connecting at a slower speed or disabling error correction.  
(With no error correction, however, line noise can cause garbage  
characters.)  
Try entering the L8 (List Online Diagnostics) command in on-line  
mode, making a screen print of the diagnostics listing, and  
checking for parameters that may be unacceptable (number of re-  
trains, round trip delay, etc.).  
My Fax and Communications Software Won’t Run at the  
Same Time  
Communications devices can be accessed by only one application at a  
time. Under DOS or Windows 3.1x, you can run either your fax software  
or your datacomm software, but not both at the same time, unless you  
have a special communications device management application. In  
Windows 95, you can have data and fax communication applications  
open at the same time, but they cannot use the same modem at the  
same time.  
146  
 
APPENDIX A: Troubleshooting  
A.2 Contacting Black Box  
A.2.1 Recording Modem Information  
Please fill in the following information on your Series II Modem on a  
photocopy of this page. This will help tech support in answering your  
questions.  
Modem Model No.:  
Modem Serial No.:  
Modem Firmware Version:  
COM Port #:  
FAX Software Type and Version:  
DataComm Software Type and Version:  
The modem model and serial numbers are silkscreened on the bottom  
of your modem. The software versions are printed on the diskette  
labels. Type ATI1 to display the modem firmware version.  
Please note the status of your modem before calling tech support. This  
status can include LED indicators, screen messages, diagnostic test  
results, problems with a specific application, etc. Use the space below  
to note modem status:  
147  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
A.2.2 Making the Call  
If you determine that your Series II Modem is malfunctioning, do not  
attempt to alter or repair the unit. It contains no user-serviceable parts.  
Call Black Box Technical Support at 724-746-5500.  
Before you do, make a record of the history of the problem. We will  
be able to provide more efficient and accurate assistance if you have  
a complete description, including:  
the information requested in Section A.1.  
the nature and duration of the problem.  
when the problem occurs.  
the devices/components involved in the problem.  
any particular application that, when used, appears to create the  
problem or make it worse.  
the results of any testing you’ve already done.  
A.3 Shipping and Packaging  
If you need to transport or ship your Series II Modem:  
Package it carefully. We recommend that you use the original  
container.  
If you are shipping the Modem for repair, make sure you include  
the phone/line cords and power supply you’re using with it. If you  
are returning the Modem, make sure you include everything you  
received with it. Before you ship, contact Black Box to get a Return  
Authorization (RA) number.  
148  
 
APPENDIX A: Troubleshooting  
A.4 Upgrading the Series II Modem’s Firmware  
The Series II Modem has a Flash PROM which contains firmware code  
for the hardware and DSP code for the digital signal processor chips. At  
various times, we may add enhancements and/or fixes to the firmware.  
The flash technology used in the Series II Modem lets you load these  
upgrades into the PROM or DSP chips through the modem's serial  
port. If a Black Box Tech Support technician tells you that you need  
to upgrade your firmware, do so, taking these steps:  
1. Follow the technician’s instructions for downloading  
FLASHPRO.ZIP and a new .HEX file from Black Box.  
2. Unzip the FLASHPRO.ZIP file. Place this unzipped file and the  
.HEX file in the same directory.  
3. Run FlashPro by typing FLASHPRO, a space, -M and hitting  
ENTER at the DOS prompt.  
4. Highlight the "Configure" option in the MAIN MENU and hit  
ENTER. Highlight "Active Port" and select the COM port to which  
you have your modem attached. Highlight "Baud Rate" and select  
the rate you want to program at. Hit ESC when finished.  
5. Highlight the "Select File to Program" option in the MAIN MENU.  
Highlight the .HEX file. Hit ESC when finished.  
6. Highlight "Program Firmware" option in the MAIN MENU. When  
you are prompted to confirm the file to program, press "Y".  
7. If you need more assistance programming FLASHPRO, then  
contact our tech support department again.  
149  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Appendix B - Dial Pulse and Tone-Dial Frequencies  
Dial Pulses  
B
Closed  
Open  
A
Digit 2  
Digit 1  
In the example above, the digit 2 is pulse dialed, followed by the digit 1.  
Each pulse consists of an A mSec open and a B mSec closed, where A  
will be either 60 or 67 mSec and B will be either 40 or 33 mSec, for a  
total of 100 mSec per pulse, or a rate of 10 pulses per second. The  
interdigital pause time is 800 mSec The pulse ratios are controlled  
by the &P command.  
Tone Dial Frequencies  
Hz  
Digits  
697  
1
4
7
2
5
8
3
6
9
A
B
C
770  
852  
941  
Hz  
*
0
#
D
1209  
1336  
1477  
1633  
150  
 
APPENDIX C: Command Summary  
Appendix C - Command Summary  
Command Values  
Description  
AT  
Attention Code that precedes most comd.  
strings except A/, A: and Escape Codes.  
RETURN  
Pressing RETURN key executes most  
commands.  
$
In Dial Comd.  
This symbol placed in dialing string enables  
the modem to detect AT&T's "call card"  
tones for accessing user's calling card to  
originate an on-line connection.  
A
Answer call, even if no ring present. Repeat  
last command. (Do not precede this  
command with AT. Do not hit RETURN to  
execute.)  
A:  
Continuous redial of last number until  
answered.  
A/  
Repeat previous command. (Do not  
precede this command with AT.)  
$An  
n = 0 or 1  
*$A0 discards data during auto-reliable time  
period.  
$A1 buffers data during auto-reliable time  
period.  
#An  
n = 0 thru 3  
*#A0 selects initial handshake at 33,600 to  
31,200 to 28,800 to 24000 to 21,600 to  
19,200 to 16,800 to 14,400 to 12,000 to 9600  
to 4800 to 2400 to 1200 to 300 bps.  
#A1 selects initial handshake at 33,600 bps  
only.  
#A2 selects initial handshake at 33,600 to  
31,200 to 28,800 to 24000 to 21600 to  
19,200 to 16,800 19,200 to 14,400 to 9600  
to 4800 bps.  
#A3 selects initial handshake at 2400 to  
1200 to 300 bps.  
* Factory Default Setting  
151  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Command Values  
Description  
&Bn  
n = 0 or 1  
*&B0 means normal transmit buffer size.  
&B1 means reduced transmit buffer size.  
&BSn  
n = 0 or 1  
&BS0 means maximum transmit block size  
of 64 characters.  
*&BS1 means maximum transmit block size  
of 256 characters.  
$BAn  
&Cn  
n = 0 or 1  
n = 0,1,2,4  
*$BA0 means speed conversion is on.  
$BA1 means speed conversion is off.  
&C0 forces Carrier Detect on.  
*&C1 lets Carrier Detect act normally.  
&C2 lets Carrier Detect drop S24 time on  
disconnect.  
&C4 resets modem when Carrier Detect  
drops.  
&CDn  
Ds  
n = 0 or 1  
*&CD0 execute cleardown on disconnect.  
&CD1 do not execute cleardown on  
disconnect.  
s = phone #  
Dial a telephone number “s,” where s may  
include up to 60 digits or T, P, R, comma  
and ; characters.  
* Factory Default Setting  
Command Values  
Description  
DsNd  
s = phone #  
d = 0 thru 9  
Store telephone number. To store, phone  
number ”s“ is entered and followed by N  
and then Directory Number “d.”  
&Dn  
n = 0 thru 3  
&D0 DTR is ignored.  
&D1 means modem returns to command  
mode.  
*&D2 lets modem react to DTR normally.  
&D3 causes modem to reset to modem  
default parameters.  
152  
 
APPENDIX C: Command Summary  
%DFn  
%DPn  
n = 0 or 1  
n = 0 or 1  
*%DF0 Line Probe Data in Graph Format.  
%DF1 Line Probe Data in Table Format.  
*%DP0 do not read Line Probe  
Information from DSP during handshaking.  
%DP1 read Line Probe Information from  
DSP during handshaking.  
$Dn  
En  
n = 0 or 1  
n = 0 or 1  
*$D0 disables DTR Dialing.  
$D1 enables DTR Dialing.  
E0 means do not echo Command Mode  
Character.  
*E1 means do echo Command Mode  
characters.  
* Factory Default Setting  
Command Values  
Description  
&En  
n = 0 thru 15  
&E0 means no error correction.  
*&E1 means V.42 Auto-reliable Mode.  
&E2 means V.42 Reliable Mode.  
&E3 means no modem-initiated flow  
control.  
*&E4 means CTS modem-initiated flow  
control.  
&E5 means Xon/Xoff modem-initiated flow  
control.  
*&E6 means Xon/Xoff not passed through.  
&E7 means Xon/Xoff passed through.  
*&E8 means Enq/Ack pacing off.  
&E9 means Enq/Ack pacing on.  
*&E10 means Normal Mode flow control  
off.  
&E11 means Normal Mode flow control on.  
&E12 means Pacing off.  
*&E13 means Pacing on.  
&E14 means data compression disabled.  
*&E15 means data compression enabled.  
153  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
$En  
*$E0 disables error correction at 300 bps.  
$E1 enables Autoreliable Mode at 300 bps.  
$E2 enables Reliable Mode at 300 bps.  
$EBn**  
%En  
n = 0 or 1  
*$EB0 enables 10 bit mode.  
$EB1 enables 11 bit mode.  
n=0 thru 5  
% E0 = Modem Won’t Escape.  
*% E1 = +++ Method (default setting).  
% E2 = Break Method.  
% E3 = Either +++ or Break Method.  
% E4 = No "OK" Response to +++  
% E5 = "OK" Response to +++  
* Factory Default Setting  
** 336 Model (MD1641A) Only  
Command Values  
Description  
#Fn  
n = 0 thru 2  
#F0 means no fallback when on-line.  
#F1 means fallback from 33600 to 4800 bps  
when on-line (increments of 2400 bps).  
*#F2 means fallback to 4800 bps from 33.6K  
bps/fall forward if line improves  
(increments of 2400 bps).  
&Fn  
n = 0, 8 or 9  
&F loads factory default values from ROM.  
*&F8 reads factory default values and switch  
settings when &F is issued.  
&F9 reads parameters stored in non-volatile  
memory when &F is issued.  
$FCn**  
$Fn  
n = 0 or 1  
n = 0 or 1  
$FC0 means no transmit of 5 second  
2100Hz signal.  
*$FC1 transmits 5 second 2100Hz signal.  
$F0 means do not fall back to normal  
connect if CR received.  
*$F1 means fall back to normal connect if  
CR received.  
154  
 
APPENDIX C: Command Summary  
&Gn  
n = 0, 1 or 2  
*&G0 turns off CCITT guard tones.  
&G1 turns on CCITT 550 Hz guard tone.  
&G2 turns on CCITT 1800 Hz guard tone.  
Hn  
n = 0 or 1  
H0 means Hang Up (go on hook).  
H1 means Go Off Hook.  
$Hn  
n = 1 thru 3  
$H1 brings up Help Screen #1.  
$H2 brings up Help Screen #2.  
$H3 brings up Help Screen #3.  
In  
n = 0,1or 2  
Read Only  
I0 requests modem ID #.  
I1 requests firmware revision #.  
I2 for MTS internal use.  
I9  
Command enables display of Windows 95  
Autodetect characteristics  
* Factory Default Setting  
** 336+ Model (MD1640A) Only  
Command Values  
Description  
L
Lists all stored telephone numbers in  
memory.  
L5  
L6  
L7  
L8  
L9  
L10  
L5 lists all current operating parameters.  
L6 lists all current S-Register values.  
L7 lists additional parameters.  
L8 lists On-Line Diagnostics.  
L9 Displays Signal Strength Information.  
L10 Displays Signal to Noise Ratio  
Information.  
L11  
L11 Displays Noise Information.  
155  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
#Ln  
n = 0 thru 3  
*#L0 means modems negotiate V.42 Mode.  
#L1 means MNP on and LAP-M off.  
#L2 means LAP-M on and MNP off.  
#L3 means no detection phase but go  
directly to LAP-M.  
* Factory Default Setting  
Command Values  
Description  
Mn  
n = 0 thru 3  
M0 means Monitor speaker always Off.  
*M1 means Monitor speaker On until  
carrier detected  
M2 means Monitor speaker always On.  
M3 Monitor speaker on during dialing/off  
during handshaking.  
$MBn  
n = speed  
$MB300 selects 300 bps on-line.  
$MB1200 selects 1200 bps on-line.  
$MB2400 selects 2400 bps on-line.  
$MB4800 selects 4800 bps on-line.  
$MB9600 selects 9600 bps on-line.  
$MB14400 selects 14400 bps on-line  
$MB19200 selects 19200 bps on-line  
$MB28800 selects 28800 bps on-line  
*$MB33600 selects 33600 bps on-line  
&Mn  
Nd  
n = 0 or 1  
*&M0 selects Async when on-line.  
&M1 selects Sync when on-line.  
d = 0 thru 9  
d = 0 thru 9  
Dial stored telephone number “d” (Do not  
include the letter D in this command.)  
NdNe  
Number Linking. If first number dialed  
(“d”)  
e = any other  
number 0  
thru 9  
is busy, another stored number (“e”) may  
be automatically dialed.  
O
Exit Command Mode and go into On-Line  
Mode.  
156  
 
APPENDIX C: Command Summary  
P
In Dial Comd.  
n = 0 or 1  
*Modem will pulse-dial numbers following  
the P.  
&Pn  
#Pn  
*&P0 means 60-40 pulse ratio.  
&P1 means 67-33 pulse ratio.  
n = 0, 1, or 2  
*#P0 selects no parity.  
#P1 selects odd parity.  
#P2 selects even parity.  
* Factory Default Setting  
Command Values  
Description  
Qn  
n = 0, 1 or 2  
*Q0 means Result Codes sent.  
Q1 means Result Codes will be suppressed  
(quiet).  
Q2 means Dumb Answer Mode.  
&Qn  
Rn  
n = 0 or 1  
n = 0 or 1  
*&Q0 selects Series II command set.  
&Q1 selects AT command set.  
*R0 means modem will not reverse modes.  
(In Dial Comd.) R1 means modem will reverse modes.  
&Rn  
n = 0, 1 or 2  
&R0 lets Clear to Send act normally.  
*&R1 forces Clear to Send on.  
&R2 drops for 1 second on disconnect.  
&RP  
$Rn  
Command Initiates a Retrain that makes  
the processor read Line Probe Information  
(valid only in V.34 mode).  
n = 0 or 1  
n = 0 or 1  
*$R0 means disconnect after 12 retransmits.  
$R1 means do not disconnect after 12  
retransmits.  
&RFn  
&RF0 selects CTS follows RTS.  
*&RF1 selects CTS to act independently  
* Factory Default Setting  
157  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Command Values  
Description  
Sr=n  
r = 0-11, 13,  
15-19, 24-26,  
Sets value of Register “r” to value of “n”,  
where “n” is entered in Decimal format.  
29, 30, 32, 34...  
Sr?  
r = 0-11, 13,  
15-19, 24-26,  
30, 32 or 34...  
Reads value of Register “r” and displays  
value in 3-digit Decimal format.  
$SBn  
n = speed  
$SB300 selects 300 bps at serial port.  
$SB1200 selects 1200 bps at serial port.  
$SB2400 selects 2400 bps at serial port.  
$SB4800 selects 4800 bps at serial port.  
$SB9600 selects 9600 bps at serial port.  
$SB19200 selects 19,200 bps at serial port.  
$SB38400 selects 38,400 bps at serial port.  
$SB57600 selects 57600 bps at serial port.  
*$SB115200 selects 115200 bps at serial  
port.  
&SFn  
&Sn  
n = 0 or 1  
*&SF0 selects DSR follows CD.  
&SF1 selects DSR independent.  
n = 0, 1 or 2  
&S0 forces Data Set Ready On.  
*&S1 lets Data Set Ready act normally.  
&S2 Data Set Ready drop is regulated by  
S24 on disconnect.  
$SPn  
n = 0 or 1  
*$SP0 disables UUCP Spoofing  
$SP1 enables UUCP Spoofing  
* Factory Default Setting  
158  
 
APPENDIX C: Command Summary  
Command Values  
Description  
T
In Dial Comd.  
Modem will tone-dial numbers following  
the T.  
&Tn  
n = 4 or 5  
&T4 means Enable Response to Request for  
Remote Digital Loopback.  
*&T5 means Disable Response to Request  
for Remote Digital Loopback.  
#Tn  
Un  
n = 0 or 1  
#T0 turns off Trellis Coded Modulation  
*#T1 turns on Trellis Coded Modulation  
n = 0, 1, 2, or 3  
U0 places modem in Analog Loop  
Originate Mode.  
U1 places modem in Analog Loop Answer  
Mode.  
U2 places modem in Remote Digital  
Loopback test mode.  
U3 places modem in Local Digital  
Loopback test mode.  
$VDn  
Vn  
n= 0 or 1  
n = 0 or 1  
*$VD0 disables Voice/Data Dialing  
$VD1 enables Voice/Data Dialing  
V0 means Result Codes sent as digits (terse  
response).  
*V1 means Result Codes sent as words  
(verbose response).  
#Vn**  
n = 0 or 1  
#V0 enables V.32terbo handshaking process  
#V1 disables V.32terbo handshaking process  
W
In Dial Comd.  
n = 0 or 1  
Wait for new dial-tone.  
&Wn  
&W0 causes modem to store its current  
parameters in non-volatile RAM, and  
modem will load these for future sessions  
instead of reading factory ROM defaults,  
unless &F command used.  
*&W1 causes modem to not store  
parameters.  
* Factory Default Setting  
** 336 Model (MD1641A) Only  
159  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Command Values  
Description  
Xn  
n = 0,1,2,3 or 4  
*X0 selects Basic Result Codes (w/o  
CONNECT 1200, CONNECT 2400).  
X1 selects Extended Result Codes  
(w/CONNECT 1200, CONNECT 2400).  
X2 selects Standard AT Command set  
with NO DIAL TONE.  
X3 selects Standard AT Command set  
with BUSY.  
X4 selects Standard AT Command set  
with NO DIAL TONE and BUSY.  
&Xn  
#Xn  
Yn  
n = 0, 1, or 2  
n = 0 or 1  
*&X0 has sync clock controlled by DIP  
switch.  
&X1 forces external sync clocking.  
&X2 forces slave sync clocking.  
*#X0 selects single XOFF character sent  
until XON level returns.  
#X1 selects multiple XOFF characters  
after buffer level is full.  
n = 0 or 1  
*Y0 disables sending or responding to  
(In Dial Command) long space “break”.  
Y1 enables sending or responding to long  
space “breaks”.  
Z
All configuration parameters are reset to  
default values.  
,
In Dial Command Causes pause during dialing.  
;
In Dial Command Causes return to Command Mode after  
dialing.  
!
In Dial Command Causes modem to flash On-Hook.  
@
In Dial Command Causes modem to wait for ringback, then  
5 seconds of silence before processing  
next part of command.  
* Factory Default Setting  
160  
 
APPENDIX C: Command Summary  
Command  
Values Description  
+++AT<CR>  
In-band Escape Sequence. Places modem in  
Command Mode while still remaining On-  
Line. Enter +++ followed by the letters A  
and T, up to ten command characters, and  
a RETURN.  
BREAK AT<CR>  
Out-of-band Escape Sequence. Places  
modem in Command mode while still  
remaining On- Line. Enter a BREAK signal,  
followed by the letters A and T, up to sixty  
command characters, and hit RETURN.  
Callback Security/Remote Configuration Command Summary  
Command  
#DBn  
Description  
#DB0 disables Callback Security and answering Yes  
to the prompt turns off Callback Security and  
erases stored phone numbers and passwords.  
Answering No to the prompt aborts the command.  
#DB1 activates remote and local password security.  
#DB2 activates remote password security.  
#CBNyyxxxxxx  
Callback password with xxxxxx being callback  
password and yy being the memory location.  
Callback password xxxxxx must start with a non-  
numeric character and upper/lower case sensitive.  
Callback password xxxxxx must be a minimum of  
6 and maximum of 10 characters. yy memory  
locations are from 0 to 29. Must specify P (pulse)  
or T (tone) dialing in string.  
+ - Dxxxxxx???Nxx  
Callback Phone Numbers xxxxxx with the +  
preceding the phone number indicating the  
callback modem phone number for the  
corresponding password at the same memory  
161  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
location. The (-) preceding the phone number  
enables direct entry when the caller uses the  
correct password without the callback modem  
having to return the call. The ??? entry at the end  
of the phone number represents an extension  
added to the main phone number. The Nxx is the  
memory location of the callback phone number  
and password.  
#Pn  
Parity of the prompt messages sent by the callback  
modem.  
#P0 is no parity  
#P1 is odd parity  
#P2 is even parity  
Command  
#RCBNxx  
Description  
Erases the callback password stored at memory  
location xx. Memory locations are 0 to 29.  
#RDNxx  
Erases the callback phone number stored at  
memory location xx. Memory locations are 0 to 29.  
Password Command Summary  
Command  
Description  
#Ixxxxxxxxxx  
Login Password is any keyboard characters (x)  
(upper/lower case sensitive), minimum 6 and  
maximum 10 characters. The default Login  
Password is #IBLACK BOX.  
#Syyyyyyyyyy  
Setup Password is any keyboard characters (y)  
(upper/lower case sensitive), minimum 6 and  
maximum 10 characters. The default Setup  
Password is #SMODEMSETUP.  
162  
 
APPENDIX C: Command Summary  
V.25bis Commands  
Command  
Description  
$Vn  
$V0 returns modem to AT command mode when  
in V.25bis mode.  
$V1 enables V.25bis mode of operation.  
$V2 allows modem to receive one V.25bis  
command while in AT command mode without  
leaving AT command mode.  
$V5 DSR follows DTR in V.25bis mode.  
$V6 DSR does not follow DTR in V.25bis mode.  
CSPs  
Changes the serial bps rate.  
CSP0300 - 300 bps  
CSP1200 - 1200 bps  
CSP2400 - 2400 bps  
CSP4800 - 4800 bps  
CSP9600 - 9600 bps  
CSP19200 - 19200 bps  
CSP38400 - 38400 bps  
CSP57600 - 57600 bps  
CSP115200 - 115200 bps  
CRNdd  
Dials phone number dd where dd can be up to  
20 characters (0 through 9, *, #, P, T and :). Phone  
number is checked against the Delayed and  
Forbidden Number lists before dialed.  
CRIdd;nn  
DIC or CIC  
Dials dd same as CRN Command and ignores nn  
identification string. The disregard or connect to  
incoming calls commands are used for auto-  
answer operations.  
DIC stops the modem from answering incoming  
calls.  
CIC causes the modem to answer incoming calls.  
163  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Appendix D - DIP-Switch Summary  
Asynchronous Mode  
DIP-Switch Condition  
Effect  
#1  
UP*  
Down  
DTR dependent on interface  
DTR forced On at all times  
#2  
UP*  
Down  
Hardware Flow Control  
Xon/Xoff Flow Control  
#3  
UP  
Down*  
-15 dB Transmission (leased line)  
-9 dB Transmission (leased line)  
#4  
UP*  
Down  
UUCP Spoofing Off  
UUCP Spoofing On  
#5  
UP*  
Down  
Automatic Answer On  
Automatic Answer Off  
#6  
UP*  
Down  
Max throughput On  
Max throughput Off  
#7  
UP  
Down*  
RTS dependent on Interface  
RTS forced On at all times  
#8  
UP  
Down*  
Disable Command Mode  
Enable Command Mode  
#9  
UP  
Down*  
Local Digital Loopback On  
Remote Digital Loopback On  
#10  
#11  
#12  
UP*  
Down  
Dial-Up Operation  
Leased Line Operation  
UP  
Down*  
"AT" Responses  
Series II Responses  
UP  
Down*  
Synchronous Mode On  
Asynchronous Mode On  
*Factory Default Setting  
164  
 
APPENDIX D: DIP-Switch Summary  
Synchronous Mode  
DIP-Switch Condition  
Effect  
#1  
#2  
#3  
#4  
#5  
#6  
#7  
#8  
#9  
#10  
UP*  
Down  
DTR Dependent On interface  
DTR forced On at all times  
UP*  
Down  
SDLC Mode On  
BSC Mode On  
UP  
Down*  
Command Mode Response Off  
Command Mode Response On  
UP*  
Down  
AS/400 Mode Off  
AS/400 Mode On  
UP*  
Down  
Answer Mode On  
Originate Mode On  
UP*  
Down  
Slave Clocking Off  
Slave Clocking On  
UP  
Down*  
RTS Dependent on interface  
RTS forced on at all times  
UP  
Down*  
Command Mode Off  
Command Mode On  
UP  
Down*  
Local Digital Loopback On  
Remote Digital Loopback On  
UP*  
Dial-Up Operation  
165  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Down  
Leased Line Operation  
#11  
#12  
UP  
Down*  
External Clock selected  
Internal Clock selected  
UP  
Down*  
Synchronous Mode On  
Asynchronous Mode On  
*Factory Default Setting  
DIP Switches #13-16  
DIP-Switch Condition  
Effect  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
UP/UP*  
28.8 K bps Operation  
19.2 K bps Operation  
14.4K bps Operation  
9600 bps Operation  
Down/UP  
UP/Down  
Down/Down  
Note: The modem baud rate command (e.g.,$MB33600) overrides the  
setting of these speed selection switches (DIP switches #13 and #14).  
#15  
UP*  
Down  
CD/DSR from Interface (Sync & Async)  
CD/DSR Forced On  
#16  
UP  
Down*  
2-Wire Leased Line (Sync & Async)  
4-Wire Leased Line  
* Factory Default Setting  
166  
 
APPENDIX E: S-Register Summary  
Appendix E - S-Register Summary  
S-REG. UNIT  
RANGE DEFAULT DESCRIPTION  
S0  
S1  
S2  
Rings  
Rings  
ASCII  
0-255  
0-255  
0-127  
1
Sets number of rings  
before modem answers.  
0
Counts rings which have  
occurred.  
43  
Sets Escape Code  
character (default is  
plus “+” sign).  
S3  
S4  
ASCII  
ASCII  
0-127  
0-127  
13  
10  
Sets character recog-  
nized as RETURN  
(default is CTRL-M).  
Sets character  
recognized as LINE  
FEED (default is CTRL-  
J).  
S5  
ASCII  
0-32,127  
8
Sets character recog-  
nized as BACKSPACE  
(default is CTRL-H).  
S6  
S7  
Seconds 2-255  
Seconds 1-255  
2
Determines wait-time  
for dial tone.  
45  
Determines how long  
modem waits for carrier  
before aborting call.  
S8  
S9  
Seconds 0-255  
100 mSec 1-255  
2
6
Sets pause time caused  
by a comma character in  
a dial command.  
Sets carrier detect  
response time.  
167  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S-REG. UNIT  
RANGE DEFAULT DESCRIPTION  
S10  
100 mSec 1-255  
7
Sets delay time between  
when carrier is lost and  
when modem  
disconnects.  
S11  
S13  
S15  
1 mSec  
ASCII  
1-255  
0-127  
70  
37  
20  
Sets time duration of  
and spacing between  
tones in tone-dialing.  
Defines Remote  
Configuration Escape  
Character  
Seconds 10-255  
Attempts 1-255  
Defines time delay for  
Callback attempts after  
initial passwords have  
exchanged.  
S16  
4
Defines the number of  
Callback attempts after  
initial passwords have  
exchanged between  
modems.  
S17  
S18  
10 mSec 0-2.5  
250 mSec Defines length of break  
time (space) to PC.  
30 min  
10-255  
30  
Defines how often  
leased-line is checked  
and restoral attempted.  
S19  
Minutes 0-255  
1
Timer used in dial  
backup mode. Specifies  
time duration modem  
attempts to restore  
leased line connection.  
168  
 
APPENDIX E: S-Register Summary  
S-REG. UNIT  
RANGE DEFAULT DESCRIPTION  
S24  
S25  
S26  
S29  
50 mSec 0-255  
20  
Sets DSR/CTS/CD  
dropout time. Default  
(20) equals one second.  
100 mSec 0-255  
0
Sets DTR dropout time.  
0 default equals  
50 mSec.  
Failed  
Attempts  
0-255  
1-255  
0
Specifies number  
of failed password  
attempts allowed.  
1
20  
Specifies the amount of  
idle time can elapse  
between AT commands  
after the SETUP  
password has been  
entered  
S30  
S32  
Minutes 0-255  
100mSec 0-255  
0
Inactivity timer used to  
disconnect modem.  
20  
Sets time that modem  
waits for a <RETURN> to  
be entered during  
escape sequence  
execution.  
S34  
Chars.  
0-60  
10  
Buffer size for number  
of characters in AT  
command string after  
on-line escape sequence,  
before buffer is cleared  
and escape sequence  
aborted.  
169  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
S-REG. UNIT  
RANGE  
DEFLT. DESCRIPTION  
S36  
S37  
S48  
Seconds 0-255  
0
5
0
S36 sets the time  
between DTR inactive  
and the modem going  
off-hook (busy-out).  
Seconds 0-255  
S37 sets the time allowed  
DTR active and the  
modem responding on-  
hook (not busy).  
N/A  
33, 31,  
S48 sets speed modem  
connects within scope  
of Enhanced V34 mode  
(e.g., S48 = 21 means  
maximum connect  
speed is 21.6K). This  
register is useful when  
line conditions will not  
support higher V34  
speeds. The default  
value is 0, which  
28, 26, 24,  
21, 19, 16,  
14, 12, 96  
and 48  
indicates a connection  
attempt of 28.8K.  
170  
 
APPENDIX F: Result Code Summary  
Appendix F - Result Code Summary  
TERSE  
(Digit)  
VERBOSE  
(Words)  
Effect  
0
1
2
3
4
5
OK  
Command was executed without  
error; ready for next command.  
CONNECT  
RING  
Modem has detected carrier and  
gone on-line.  
Modem has detected ring caused  
by incoming call.  
NO CARRIER  
ERROR  
No carrier signal has been detected  
within allowed time.  
Error in Command line (too many,  
or invalid, characters).  
CONNECT 1200  
Modem has detected carrier at  
1200 bps and gone on-line.  
6
7
8
9
NO DIAL TONE  
BUSY  
No dial tone has been detected.  
A busy signal has been detected.  
Remote system did not answer.  
NO ANSWER  
CONNECT 2400  
Modem has detected carrier at  
2400 bps and gone on-line.  
11  
12  
13  
CONNECT 4800  
CONNECT 9600  
Modem has detected carrier at  
4800 bps and gone on-line.  
Modem has detected carrier at  
9600 bps and gone on-line.  
CONNECT 14400 Modem has detected carrier at  
14400 bps and gone on-line.  
171  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
TERSE  
(Digit)  
VERBOSE  
(Words)  
Effect  
19  
21  
24  
26  
28  
31  
33  
CONNECT 19200 Modem has detected carrier at  
19200 bps and gone on-line.  
CONNECT 21600 Modem has detected carrier at  
21600 bps and gone on-line.  
CONNECT 24000 Modem has detected carrier at  
24000 bps and gone on-line.  
CONNECT 26400 Modem has detected carrier at  
26400 bps and gone on-line.  
CONNECT 28800 Modem has detected carrier at  
28800 bps and gone on-line.  
CONNECT 31200 Modem has detected carrier at  
31200 bps and gone on-line.  
CONNECT 33600 Modem has detected carrier at  
33600 bps and gone on-line.  
Note: If Series II Modem is used in MNP Reliable mode, the following  
responses change:  
1R  
CONNECT RELIABLE  
5R  
9R  
CONNECT 1200 RELIABLE  
CONNECT 2400 RELIABLE  
CONNECT 4800 RELIABLE  
CONNECT 9600 RELIABLE  
CONNECT 14400 RELIABLE  
CONNECT 19200 RELIABLE  
CONNECT 21600 RELIABLE  
CONNECT 24000 RELIABLE  
CONNECT 26400 RELIABLE  
CONNECT 28800 RELIABLE  
CONNECT 31200 RELIABLE  
CONNECT 33600 RELIABLE  
11R  
12R  
13R  
19R  
21R  
24R  
26R  
28R  
31R  
33R  
172  
 
APPENDIX F: Result Code Summary  
Note: If Series II Modem is used in LAP-M reliable mode, the following  
responses change:  
1L  
CONNECT LAPM  
5L  
9L  
CONNECT 1200 LAPM  
CONNECT 2400 LAPM  
CONNECT 4800 LAPM  
CONNECT 9600 LAPM  
CONNECT 14400 LAPM  
CONNECT 19200 LAPM  
CONNECT 21600 LAPM  
CONNECT 24000 LAPM  
CONNECT 26400 LAPM  
CONNECT 28800 LAPM  
CONNECT 31200 LAPM  
CONNECT 33600 LAPM  
10L  
12L  
13L  
19L  
21L  
24L  
26L  
28L  
31L  
33L  
Note 1: If the Series II Modem is used with data compression, the word  
COMPRESSED or the letter C is added to result codes.  
Note 2: If the Standard AT Command Set 2400 responses are selected  
with the &Q command, the following responses change:  
9
(not used)  
10  
CONNECT 2400  
Modem has detected carrier at  
2400 bps and  
gone on-line.  
173  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Appendix G - V.25bis Operation  
Chapter 5 described a set of commands which let the Series II Modem  
dial, hang-up, and be configured for various applications. However,  
these commands, the AT command set, are only functional when the  
DTE transmits data asynchronously. That is, they cannot be used with  
synchronous equipment such as that found in IBM's Binary Synchro-  
nous Communications (BSC) and Synchronous Data Link Control  
(SDLC)* environments.  
The ITU V.25bis commands provide you with an alternate set of com-  
mands and responses to those described in Chapter 5 for applications  
in which the DTE is synchronous. V.25bis commands support dialing  
functions in asynchronous or synchronous mode according to the rec-  
ommendations of the ITU; however, the AT commands are understood  
to reign in the asynchronous world, while the V.25bis commands are  
relegated to the synchronous world of datacomm. If you need to  
establish a datacomm link over Public Switched Telephone Network  
(PSTN) dial-up services, and your equipment outputs a synchronous  
data stream, V.25bis commands are essential. V.25bis mode AT  
commands do not include any modem configuration commands. You  
can execute normal AT commands in V.25bis mode for modem  
configuration.  
Delayed and Forbidden Numbers  
V.25bis provides the facility to delay failed call retry attempts by putting  
numbers that failed to connect on a special Delayed Number list. Subse-  
quent dialing of these numbers will be delayed (time specified by a  
country regulation) and an appropriate message displayed. If the  
number is retried more than the maximum allowed number of times  
(number is also specified by country regulation), it is placed on the  
Forbidden Numbers list, and no further retries will be allowed. When  
the Forbidden Numbers list is full, no dialing is allowed and a CFIFF  
indication is given. The modem in AT command mode will respond  
with NO CARRIER. If country regulations require that the Forbidden  
Numbers list be checked in AT mode, then NO CARRIER will be the  
response to a dial attempt in AT mode. Numbers will also be put on the  
Forbidden Numbers list if the Delayed Numbers list is full and a new  
number fails for the first time. In that case, the new number will be  
174  
 
APPENDIX G: V.25bis Operation  
added to the Delayed Number list and the oldest existing number  
added to the Forbidden Numbers list. Numbers are removed from the  
Forbidden Numbers list by after a certain time has past (also by country  
regulation).  
Some country regulations have numbers remain on the Forbidden  
Numbers list permanently. The Delayed Number and Forbidden  
Numbers lists are eight numbers long (20 characters each).  
V.25bis Operation  
Operation in V.25bis mode is similar to AT command mode in that  
certain DIP-Switch functions are important to its operation. V.25bis does  
not include any speed detection for asynchronous mode, so when you  
are giving commands, you must stay in your initial speed (i.e., if you  
change your terminal speed while entering an AT command, you will  
get no responses). In synchronous mode, the modem supplies the  
clock, so the synchronous terminal “knows” the speed.  
You must be in V.25bis mode for the commands described here to  
function. Most AT commands will also function, except those associated  
with dialing such as ATD, ATN, ATO, and ATU. To get into V.25bis mode,  
you type AT$V1. At this point your modem does no more speed or  
parity detection (things associated with asynchronous operation). To  
get out of V.25bis mode and back into AT command mode, enter  
AT$VO. The AT$V2 command allows you to run one V.25bis command  
from AT command mode without leaving AT command mode.  
There is no command to select between asynchronous and synchronous  
V.25bis operation. The position of DIP-Switch #12 selects between  
modes. For synchronous mode, DIP-Switch #12 must be UP, and the AT  
command mode enabled.  
Another asynchronous mode concern is the problem of connecting at a  
different speed than the speed at which the serial port is set. If your  
modem port speed is different from the serial port speed, you must  
either:  
1) Enable speed conversion and have flow control on, or  
2) Enable connect responses (with the ATX1 command) and change  
the serial baud rate after receiving a connect message.  
175  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
If the $VD1 command is entered when in Auto-Answer mode, the  
modem answers immediately upon receiving the first ring.  
There is no disconnect message (NO CARRIER) if a normal connection  
is made.  
V.25bis Set-Up and Initialization  
Before you operate your modem in the V.25bis mode, you need to make  
sure it is set up properly (various RS-232 lines such as DSR and CTS act  
as specified in the V.25bis standard). Setup involves proper DIP-Switch  
settings and soft-switches (software controlled conditions).  
V.25bis DIP-Switches  
#1 Unforced DTR  
#2 NA  
#3 NA  
#4 NA  
#5 Auto-Answer enabled  
#6 Async - Max throughput set  
Sync - Slave Clocking unforced  
#8 - Command Mode forced  
#9 - Digital Loopback Off  
#10 - Dial-Up  
#11 - Async - AT/Series II Resp.  
#12 - Async/Sync mode set per requirements  
176  
 
APPENDIX G: V.25bis Operation  
V.25bis Mode AT Commands  
The following commands will either alter standard V.25bis behavior (so  
you must be careful in their use) or they are not allowed, as indicated.  
All other commands can be used in V.25bis operation.  
A
Not Allowed  
A/  
A:  
Not Allowed  
Not Allowed  
D
Not Allowed  
D...N  
$D  
E
Not Allowed  
Alters Operation ($D1 in V25bis is direct call mode)  
Alters Operation  
&F  
Alters Operation (removes modem from asynchronous  
V.42bis mode)  
N
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
N...N  
O
P
T
U
W
X
Alters Operation (X0 no connect message, X1 connect  
message)  
,
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
;
!
@
+++AT<CR> Not Allowed  
177  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
V.25bis Responses (Result Codes)  
When in V.25bis mode (the AT$V1 command executed), your modem  
provides you with several responses which can help you follow the  
progress of V.25bis operations. These are similar to the Result Codes  
associated with AT Command mode operation. The V.25bis responses  
are in the form of three-character mnemonics as listed below:  
INC  
Incoming Call (same as RING indicator)  
A valid V.25bis command has been attempted  
Call delayed for t minutes (number on Delayed list)  
Call failure indicator where rr equals:  
VAL  
DLCt  
CFlrr  
et - Engaged tone (same as BUSY)  
nt - Call Answered but No Answer Tone  
ab - Call Not Answered  
fc - Number on Forbidden List  
ns - Number not stored in memory  
ua - User Abort  
nd - No Dialtone  
ff - Forbidden List full  
LSNmm;dd...dd  
LSDmm;dd...dd  
LSFmm;dd...dd  
CON ssss  
Phone number in V.25bis memory  
Phone number on the Delay list  
Phone number on the forbidden list  
Connection at ssss speed (if X1 in effect)  
V.25bis AT Commands  
The AT commands associated with V.25bis mode are described as  
follows. Note that one command enables and disables V.25bis mode and  
the rest are only operable in the V.25bis mode.  
178  
 
APPENDIX G: V.25bis Operation  
Enable/Disable V.25bis Mode ($V) Command  
The function of the $V command is to select the V.25bis mode in  
asynchronous mode. (Synchronous mode is set up with switches. For  
example, the modem could be in AT command mode, (AT$V1), and if  
synchronous mode is enabled with AT Command mode enabled, then  
V.25bis mode is selected). Prior to executing this command, make sure  
that your modem is properly set up to perform the type of operation  
you will be performing. Refer to the initialization section of this  
appendix for information about modem set-up. When in V.25bis mode,  
most normal AT commands will also function (except D,N,O and U).  
V.25bis operates in asynchronous or synchronous modes (depending on  
the position of DIP-Switch #12), and does not check for terminal speed  
(so do not change speeds while in this mode) or parity. In synchronous  
mode, speed is not important since the internal clocks provide synchro-  
nization.  
To place your modem in V.25bis mode from asynchronous mode, enter  
the AT$V1 command. To return to AT command mode, enter the  
AT$V0 command. AT$V2 allows you to run one V.25bis command from  
AT command mode without leaving AT command mode (the V.25bis  
command follows $V2 on the command line).  
Change Serial Baud Rate (CSP) Command  
The CSP command will change the serial baud rate of your modem by  
entering CSPsssss where sssss can equal:  
0300  
1200  
2400  
4800  
=
=
=
=
=
=
=
=
=
300 bps  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
19200 bps  
38400 bps  
57600 bps  
115200 bps  
9600  
19200  
38400  
57600  
115200  
179  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Dial Phone Number Provided (CRN) Command  
The CRN command permits the dialing of the phone number immedi-  
ately following it (from the command line). It is similar to the D com-  
mand of the AT command set, except that the number is first checked  
against the Delayed Number and Forbidden Number list. If permitted,  
depending on the country regulations in effect, the number will then  
be dialed. For example, if you enter CRN7859875 and hit RETURN,  
your modem will check the two lists. If the number is on the Delayed  
Numbers list, you can dial that number again after t minutes have  
passed. If the number is on the Forbidden list, a CFIFC message will be  
displayed.  
You can use various commands from the AT command set within the  
CRN command line to facilitate the dialing process, such as P, T, or :  
for pulse dialing, tone dialing and wait for dial tone. V.25bis supports  
“smart” dialing.  
To dial a phone number, enter CRNdd...dd where dd...dd is the phone  
number, which can be up to 20 characters long using any character on  
the telephone pad (0 through 9, *, #, P, T, and :).  
Some additional dialing characters may be available, based on country  
regulations.  
180  
 
APPENDIX G: V.25bis Operation  
Listing Delayed Phone Numbers (RLD) Command  
When a phone number is dialed by a CRN command and a connection  
is not made, the number is entered in the modem's V.25bis Delayed  
Number list along with the number of retry attempts. Any further  
dialing attempts will be delayed some amount of time (determined by  
the regulations of each country). While the delay is in progress, the  
modem will give a DLC indication. The list contains eight numbers.  
When filled, the next number failing “bumps” off the oldest number on  
the list onto the Forbidden Number list. Numbers on the Delayed  
Number list that succeed in a connect attempt are removed. If a certain  
number of failed attempts occur (the number of failed attempts is  
specified by each country), the number is entered into the V.25bis  
Forbidden Phone Number List. Forbidden phone numbers cannot be  
dialed at all. To list the phone numbers on the V.25bis Delayed Phone  
Number List, enter RLD and hit RETURN.  
Listing Forbidden Phone Number (RLF) Command  
Those phone numbers that have failed to connect the required number  
of times as specified by country regulations are removed from the  
Delayed Number list and entered onto the V.25bis Forbidden Number  
list. Numbers on the Forbidden Number list cannot be dialed at all for  
some maximum amount of time, which is also specified by country reg-  
ulations. In some countries, the time might be one hour, and in others  
the number may never be dialed again. The forbidden list is eight num-  
bers long, with the newest number replacing the oldest if the memory is  
full. To list the numbers in the Forbidden list enter RLF and hit  
RETURN.  
Disregard or Connect to Incoming Calls (DIC or CIC)  
Command  
The Disregard or Connect to Incoming Calls commands are used for  
Auto-Answer operations. Depending on the country regulations, your  
modem will wait some amount of time or number of rings before an-  
swering the call. During that time, you can stop the modem from  
answering the call by entering the DIC (Disregard Incoming Calls)  
command. The CIC (Connect to Incoming Calls) command will cause  
your modem to answer the call (either reversing the effect of a DIC  
181  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
command or simply have your modem answer the call immediately  
without waiting the regulation time before answering).  
DTR Dialing ($D) Command  
DTR Dialing is an alternate method of causing the Series II Modem to  
automatically dial a number. Data Terminal Ready (DTR) is a signal  
that comes into the modem from the terminal or computer to which it  
is connected via pin 20 of the RS232 interface. In DTR Dialing, the  
modem will automatically dial a stored number as soon as it receives a  
high DTR signal. The DTR Dialing method is popular when using the  
Modem in synchronous applications.  
To enable DTR Dialing, enter the command AT$D1 and hit Return. The  
modem will now dial the phone number you have stored as N0 when it  
receives a high DTR signal (see the D...N command in Chapter 5).  
DTR must remain high for the duration of the call, until disconnect.  
To disable DTR Dialing, enter the command AT$D0 (or AT$D) and hit  
RETURN.  
When you use DTR Dialing, be sure that DIP-Switch #1 is in the UP  
position, so that DTR is not forced on.  
In addition, when using DTR Dialing in a synchronous application,  
be sure that DIP-Switch #8 is in the UP position to disable V.25bis  
Command mode.  
182  
 
APPENDIX G: V.25bis Operation  
ITU V.25bis Country Specific Information  
Due to the flexibility of the V.25bis standard, each country may establish  
specific regulations governing the way operations are handled. Here  
are details about how each country's specific regulations can affect the  
operation of V.25bis in modems that the Series II Modem might  
communicate with. (This information is provided for your reference  
only; the Series II Modems are not approved for operation outside the  
U.S. and Canada.)  
1. Italy  
a) Command/Indication modifications  
1. Phone number indications include status ;ZPSTTT  
a)Z - U, D, or F, for Unrestricted, Delayed or Forbidden  
b)P - Delay time if delayed  
c)S - Number of retries so far  
d)  
TTT - Interdiction time to further attempts  
b)Delayed and Forbidden list behavior  
1. 5 retries without delay  
2. 2 minute delay between next 4 retries  
3. After 9 retries the number is put on the forbidden list  
4. 120 minute timer is started on entry to delay list  
5. When it runs out, the number is removed from which ever list  
it is on  
c)Auto-Answer mode behavior  
1. Auto-Answer in 5 seconds if no DIC  
2. Get 10 seconds after DIC to enter CIC  
3. If 10 seconds times out then no connection is possible  
183  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
2. Switzerland  
a)Command/Indication modification  
1. Modem must remain on-hook for 5 seconds after disconnect  
2. Modem must remain on-hook for 5 minutes after 4  
consecutive failed calls  
3. If modem must remain on-hook, then it is “paused”  
4. If the modem is paused and a call is attempted a PAU  
indication is given.  
a)PAUt Modem is paused for t minutes  
b)Delayed and Forbidden list behavior  
1. 2 minute delay between 4 retries  
2. After 4 retries the number is put on the forbidden list  
3. The number remains on the forbidden list forever  
c)Auto-Answer behavior  
1. Auto-Answer mode after 2 rings if no DIC  
3. Austria  
a)Command/Indication modification (none)  
b)Delayed and Forbidden list behavior  
1. No delay between retries  
2. After 2 retries to numbers that answer, but give no answer  
tone (CFINT), the number is put on the forbidden list  
3. After 10 retries with busy or no dialtone, the number is put on  
the forbidden list  
4. The number remains on the forbidden list forever  
5. Delayed and Forbidden Numbers lists are checked when  
184  
 
APPENDIX G: V.25bis Operation  
dialing in AT mode. If dialing is not possible then NO  
CARRIER is the response.  
c)Auto-Answer behavior  
1. Auto-Answer in 5 seconds if no DIC  
4. France  
a)Command/Indication modification (none)  
b)Delay and Forbidden list behavior  
1. 2 min. delay after 1st call, 4 after 2nd, 6 after 3rd, etc.  
2. After 5 retries, the number is put on the forbidden list  
3. The number remains on the forbidden list forever  
4. Delayed and Forbidden Numbers lists are checked when  
dialing in AT command mode. If dialing is not possible then  
No Carrier is the response.  
c) Auto-Answer mode behavior  
1. Auto-Answer in 5 seconds if no DIC  
5. Belgium  
a)Command/Indication modification (none)  
b)Delay and Forbidden list behavior  
1. 1 min. delay between calls  
2. After 4 retries, the number is put on the forbidden list  
3. The number remains on the forbidden list for 1 hour after  
entry to forbidden list  
4. Delayed and Forbidden Numbers lists are checked when  
dialing in AT command mode. If dialing is not possible then  
No Carrier is the response.  
c)Auto-Answer behavior  
1. Auto-Answer in 5 seconds if no DIC.  
185  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
6. Singapore  
a)Command/indication modifications  
1. Dialing digit ‘=’ means wait for dialtone (acts the same as ‘:’ in  
dialing string)  
b)Delay and Forbidden list behavior  
1. 5 retries without delay  
2. 2 minute delay between next 4 retries  
3. After 9 retries the number is put on the forbidden list  
4. 120 minute timer is started on entry to delay list  
5. When it runs out, the number is removed from whichever list it  
is on.  
186  
 
APPENDIX H: Series II modem cables  
Appendix H - Series II Modem Cables  
These cables connect your Series II Modem to the serial port of your  
terminal or computer serial port.  
DB25 DTE Connector  
DB25 DCE Connector  
on Computer, etc.  
on Modem  
TD  
2
3
2
3
4
5
6
7
8
TD  
RD  
RD  
RTS  
CTS  
DSR  
GND  
CD  
4
RTS  
CTS  
DSR  
GND  
CD  
5
6
7
8
DTR  
RI  
20  
22  
20 DTR  
22 RI  
Figure I-1. RS232 Cable (IBM PC)  
7
4
8-pin mini-DIN  
8
6
1
5
3
2
TD  
2
3
4
5
3
5
1
2
TD  
RCV  
Handshake Out  
Handshake In  
RCV  
RTS  
CTS  
GND  
7
4
8
GND  
GND  
Figure I-2. Mac Cable  
187  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
The following cables are for 2-wire and 4-wire leased line connections using  
screw connectors.  
1
2
3
Red (Tip)  
Green (Ring)  
4
5
6
To Terminal-Block Screws  
(Transmit and Receive)  
RJ-11 plug  
Figure I-3. Two Wire Leased Line Connection  
Red  
3
Transmit Pair  
Receive Pair  
Green  
Yellow  
Black  
4
2
5
To Terminal-Block Screws  
(Transmit and Receive)  
RJ-11 plug  
Figure I-4. Four Wire Leased Line Connection  
(336+ [MD1640A] Only)  
188  
 
APPENDIX I: RS232C Interface Specifications  
Appendix I - RS232C Interface Specifications  
The Series II Modem's RS232C interface circuits have been designed to  
meet the electrical specifications given in EIA (Electronic Industries  
Association) RS232C standards. All signals generated by the modem are  
approximately 10 volts when measured across a load of 3000 ohms or  
greater. The receiving circuits of the modem will accept signals in the  
3 to 25 volt range. The voltage thresholds are:  
Negative = voltage more negative than –3 volts with respect to signal  
ground  
Positive = voltage more positive than +3 volts with respect to signal  
ground  
SIGNAL INFORMATION:  
NEGATIVE  
POSITIVE  
Binary State  
Signal Condition  
Control and Timing Function  
One  
Mark  
Off  
Zero  
Space  
On  
The input impedances of all modem circuits which accept signals from  
the data processing terminal or CPU equipment have DC resistances of  
4.7K. For more specific details, consult the EIA RS232C standard itself.  
The following chart lists the EIA RS232C interface pins and circuits  
present on the Series II Modem's RS232C Interface connector. All other  
pins are unused.  
Pin  
No.  
Abbrev. EIA  
CCITT  
Signal  
Function  
Circuit Circuit Source  
1
2
3
4
5
6
7
8
PG  
SD  
--  
101  
103  
104  
105  
106  
107  
102  
109  
--  
--  
Protective Ground  
Transmitted Data  
Received Data  
Request to Send  
Clear to Send  
Data Set Ready  
Signal Ground  
Carrier Detect  
Test Voltage  
BA  
BB  
CA  
CB  
CC  
AB  
CF  
+v  
DTE  
DCE  
DTE  
DCE  
DCE  
--  
DCE  
DCE  
DCE  
DCE  
DCE  
DTE  
RD  
RTS  
CTS  
DSR  
SG  
CD  
+v  
HS  
9**  
12  
15*** TC  
17*** RC  
--  
--  
High Speed  
DB  
DD  
CD  
114  
115  
108/2  
Transmit Clock  
Receive Clock  
Terminal Ready  
20  
TR****  
189  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
22  
24  
25  
RI  
XTC  
OOS  
CE  
DA  
CN  
125  
113  
142  
DCE  
DTE  
DTE  
Ring Indicator  
External Transmit Clock  
Terminal Busy  
** Pin 9 need not be present in your RS232C cable  
*** Pins 15 and 17 are necessary only for synchronous operation  
**** Also known as DTR (Data Terminal Ready)  
The computer or terminal should be supplied with a cable terminated  
with a Cinch DB25P (or equivalent) connector mounted in a Cinch  
DB51226-1 (or equivalent) hood assembly as specified by the EIA  
RS232C standard.  
Functional Description of RS232C Signals:  
Transmitted Data - Pin 2, SD (BA)  
Direction: to modem  
Signals on this circuit are generated by the customer's terminal and  
transferred to the transmitter of the Series II Modem. A positive signal  
is a space (binary 0) and a negative signal is a mark (binary 1). The  
transmitting terminal should hold this line in the marking state when  
no data is being transmitted, including intervals between characters or  
words. The TRANSMIT (XMT) LED indicates the status of this circuit.  
Received Data - Pin 3, RD (BB)  
Direction: from modem  
The lead is the data output of the modem. Data signals received from  
the remote modem are presented on this line. When no carrier signal is  
being received (pin 8 negative), this line will be forced into a marking  
condition. The RECEIVE (RCV) LED indicates the status of this signal.  
Request To Send - Pin 4, RTS (CA)  
Direction: to modem  
The RTS signal indicates to the modem that the computer or terminal  
has data that it wants to transmit.  
190  
 
APPENDIX I: RS232C Interface Specifications  
Clear To Send - Pin 5, CTS (CB)  
Direction: from modem  
The CTS line indicates to the terminal that the Series II Modem will  
transmit any data present on the Transmit Data line (pin 2).  
Data Set Ready - Pin 6, DSR (CC)  
Direction: from modem  
DSR On indicates that the Series II Modem is in the data mode and is  
connected to the communications channel. This signal will be on  
during analog-loop-test mode.  
Signal Ground - Pin 7, SG (AB)  
The SG lead is connected to signal ground of the modem. It establishes  
the common ground reference for all other interface signals.  
Data Carrier Detect - Pin 8, CD (CF)  
Direction: from modem  
DCD On (positive voltage) indicates that data carrier has been received  
from the other modem. This circuit will not normally turn on in the  
presence of message circuit noise or out-of-band signals. There is a one  
second delay between when the carrier tone has been detected and  
when the CD circuit is turned on.  
This signal goes off if received data carrier falls below the receiver  
threshold for more than 37 mSec. When CD is off, the Received Data  
circuit (pin 3) is held to the marking state.  
Test Voltage - Pin 9, XV  
Direction: from modem  
The XV lead has 330 ohms of resistance to +12 volts DC. This lead may  
be used to strap other signals high. For example, if the terminal does  
not supply a DTR (Data Terminal Ready) signal, Pin 9 may be jumpered  
to Pin 20 (DTR) on the RS232 connector or in the cable to force DTR  
on.  
191  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Transmit Clock - Pin 15, TC (DB)  
Direction: from modem  
The TC signal is provided only when the Series II Modem is used in the  
synchronous mode. The clock is a square wave and is used to provide  
the computer or terminal with timing information for its Transmit Data  
circuit (pin 2). This clock will be provided on the interface at all times  
when the modem is in Synchronous mode.  
The first signal element of the Transmitted Data signal should be pre-  
sented by the terminal on the first positive (Off to On) transition of TC  
which occurs after the CTS circuit on pin 5 has turned on. The trans-  
mitted data is sampled by the modem on negative transition of TC.  
Receive Clock - Pin 17, RC (DD)  
Direction: from modem  
The RC signal has the same characteristic of Transmit Clock, with the  
exception that it is used to provide the computer or terminal with  
timing information for its Receive Data (pin 3) circuit. The negative  
transition (On to Off) of RC indicates the center of each signal element  
on the Received Data circuit.  
Data Terminal Ready - Pin 20, TR or DTR (CD)  
Direction: to modem  
This signal (TR or DTR) provides a means for the terminal or computer  
to control the modem's connection to the communications channel. A  
high DTR signal is required by the modem to be able to communicate.  
Turning DTR off for more than 50 mSec will force the modem to  
disconnect.  
The most common use of DTR is in automatic answer applications. A  
high DTR signal is required by the modem to answer a call. A frequently  
used method is to have the computer turn on DTR in response to RI  
(Ring Indicator), which allows the modem to answer. Later, DTR is  
192  
 
APPENDIX I: RS232C Interface Specifications  
turned off at the conclusion of the log off procedure, which forces the  
modem to disconnect, enabling it to receive another call. In non auto  
answer applications it is advisable to leave DTR on using the modem's  
DIP-switch option. This is the standard factory setting. An alternative is  
to provide a constant high DTR from the terminal or computer. The  
Data Terminal Ready (DTR) LED indicates the status of this signal.  
Ring Indicator - Pin 22, RI (CE)  
Direction: from modem  
This signal will remain on for the duration of the ringing signal. When a  
ring signal is received by the modem, the modem will automatically  
answer after the first ring. The modem will answer after a specified  
number of rings which can be programmed in AT Command mode, but  
if none is specified, the modem will answer after the first ring.  
External Transmit Clock - Pin 24, XTC  
Direction: to modem  
Supplies the same function as transmit clock on Pin 15.  
Terminal Busy (Out of Service) - Pin 25, OOS  
Direction: to modem  
The Terminal Busy (OOS) circuit is not defined in the RS232C  
standard, but is used by us and most manufacturers to make the phone  
lines busy to incoming phone calls. Pin 25 is not normally connected to  
the RS232C interface when shipped from the factory; it can be ordered  
connected as an option. If pin 25 is connected and is brought high, the  
modem will be placed Off Hook, and busy to incoming calls.  
193  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
Appendix J - Regulatory Information  
FCC and IC EMI/RFI Statements  
When correctly installed and maintained, the modem will present no  
hazard to the user. When correctly installed the modem will be  
connected to the PSTN or a PW and to a Data Terminal Equipment  
(DTE), whose modem connections comply with ITU recommendation  
V28. The DTE connections are therefore taken to be safe voltages (less  
than 30 volts).  
This equipment generates, uses, and can radiate radio frequency energy  
and if not installed and used properly, that is, in strict accordance with  
the manufacturer’s instructions, may cause interference to radio  
communication. It has been tested and found to comply with the limits  
for a Class A computing device in accordance with the specifications in  
Subpart J of Part 15 of FCC rules, which are designed to provide  
reasonable protection against such interference when the equipment is  
operated in a commercial environment. Operation of this equipment in  
a residential area is likely to cause interference, in which case the user  
at his own expense will be required to take whatever measures may be  
necessary to correct the interference.  
Changes or modifications not expressly approved by the party  
responsible for compliance could void the user’s authority to operate  
the equipment.  
This digital apparatus does not exceed the Class A limits for radio noise emission  
from digital apparatus set out in the Radio Interference Regulation of Industry  
Canada.  
Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les  
limites applicables aux appareils numériques de la classe A prescrites dans le  
Règlement sur le brouillage radioélectrique publié par Industrie Canada.  
194  
 
APPENDIX J: Regulatory Information  
FCC Part 68 Regulations for Telephone-Line  
Interconnection  
1. This equipment complies with Part 68 of the Federal Communica-  
tions Commission (FCC) rules. On the outside surface of this  
equipment is a label that contains, among other information, the  
FCC registration number and ringer equivalence number (REN).  
If requested, this information must be provided to the telephone  
company.  
2. As indicated on the next page, the suitable jack (Universal Service  
Order Code connecting arrangement) for this equipment is  
shown. If applicable, the facility interface codes (FIC) and service  
order codes (SOC) are shown.An FCC-compliant telephone cord  
and modular plug is provided with this equipment. This equipment  
is designed to be connected to the telephone network or premises  
wiring using a compatible modular jack which is Part 68 compliant.  
See installation instructions for details.  
3. The ringer equivalence number (REN) is used to determine the  
quantity of devices which may be connected to the telephone line.  
Excessive REN’s on the telephone line may result in the devices not  
ringing in response to an incoming call. In most, but not all areas,  
the sum of the REN’s should not exceed five (5.0). To be certain of  
the number of devices that may be connected to the line, as  
determined by the total REN’s, contact the telephone company to  
determine the maximum REN for the calling area.  
4. If this equipment causes harm to the telephone network, the tele-  
phone company will notify you in advance. But if advance notice  
isn’t practical, the telephone company will notify the customer as  
soon as possible. Also, you will be advised of your right to file a  
complaint with the FCC if you believe it is necessary.  
5. The telephone company may make changes in its facilities, equip-  
ment, operations, or procedures that could affect the operation of  
the equipment. If this happens, the telephone company will  
provide advance notice in order for you to make necessary  
modifications in order to maintain uninterrupted service.  
195  
 
SERIES II INTELLIGENT DATA/FAX MODEMS  
6. If trouble is experienced with this equipment (the model of which  
is indicated below) please contact Black Box at the address shown  
below for details of how to have repairs made. If the trouble is  
causing harm to the telephone network, the telephone company  
may request you remove the equipment from the network until the  
problem is resolved.  
7. No repairs are to be made by you. Repairs are to be made only by  
Black Box. Unauthorized repairs void registration and warranty.  
8. This equipment cannot be used on public coin service provided by  
the telephone company. Connection to Party Line Service is subject  
to state tariffs. (Contact the state public utility commission, public  
service commission or corporation commission for information.)  
9. If so required, this equipment is hearing-aid compatible.  
Trade Names:  
Model Number:  
Series II Modem 336 and 336+  
Series II Modem 336: MD1641A  
Series II Modem 336+: MD1640A  
AU7USA-20673-MM-E  
0.3B  
FCC Registration #:  
Ringer Equivalence:  
Modular Jack (USOC):  
Service Center in USA:  
RJ11C or RJ11W (single line)  
Black Box Corp.  
1000 Park Dr.  
Lawrence, PA 15055-1018  
U.S.A.  
Phone: (724) 746-5500  
Fax: (724) 746-0746  
WWW: www.blackbox.com  
196  
 
APPENDIX J: Regulatory Information  
Canadian Limitations Notice  
Notice: The ringer equivalence number (REN) assigned to each  
terminal device provides an indication of the maximum number of  
terminals allowed to be connected to a telephone interface. The  
termination of a interface may consist of any combination of devices  
subject only to the requirement that the sum of the ringer equivalence  
numbers of all the devices does not exceed 5.  
Notice: The Industry Canada label identifies certificated equipment.  
This certification means that the equipment meets certain telecommu-  
nications network protective, operational and safety requirements. The  
Industry Canada does not guarantee the equipment will operate to the  
user’s satisfaction.  
Before installing this equipment, users should ensure that it is permissi-  
ble to be connected to the facilities of the local telecommunications  
company. The equipment must also be installed using an acceptable  
method of connection. The customer should be aware that compliance  
with the above conditions may not prevent degradation of service in  
some situations.  
Repairs to certified equipment should be made by an authorized  
Canadian maintenance facility designated by the supplier. Any repairs  
or alterations made by the user to this equipment, or equipment  
malfunctions, may give the telecommunications company cause to  
request the user to disconnect the equipment.  
Users should ensure for their own protection that the electrical ground  
connections of the power utility, telephone lines and internal metallic  
water pipe system, if present, are connected together. This precaution  
may be particularly important in rural areas.  
Caution: Users should not attempt to make such connections them-  
selves, but should contact the appropriate electric inspection authority,  
or electrician, as appropriate.  
197  
 
© Copyright 2000. Black Box Corporation. All rights reserved.  
1000 Park Drive • Lawrence, PA 15055-1018 • 724-746-5500 • Fax 724-746-0746  
 

Black Decker Laser Level BDL400S User Manual
Black Decker Power Screwdriver 618492 01 User Manual
Blodgett Electric Steamer SB 6E User Manual
Bogen Car Amplifier GA6A User Manual
Bosch Appliances Washer LOGIXX 9 User Manual
Bosch Appliances Washer WFR 2450 User Manual
Bosch Power Tools Saw T4B User Manual
Bush Hog Lawn Mower RMB 1660 User Manual
Casio Digital Camera EX M20 User Manual
Chicago Electric Saw 41168 User Manual