18
MultiModemBA User Guide
3.1 Introduction
Chapter 2 described the installation of PhoneTools, a communications software. If you are using a
different software package, there are some points you should take into consideration. 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
MultiModem. The last section of this chapter walks you through the basics of using your modem.
3.2 Configuring Your Software
Communications software must be configured to work with your modem, 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.
3.2.1 Configuring Software for Your Modem
Because remote computers may have different connection requirements 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. Most communications 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

AT

tention 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 MultiModem does not appear on a modem list, you may use the
MultiModemII initialization string.
3.4 PC Initialization Strings
We recommend the following initialization string for a MultiModem 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 extended 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 MultiModem on a telephone line that functions solely as a

DATA

LINE

:
AT &F X4 S0= 2 ^M