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MultiModemBA User Guide
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
3.4.1 Changing Default Parameters
By default, the 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>
This string selects the factory default parameters, then turns auto-answer off and stores that setting,
along with all other current parameters, 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 (AT S0=1^M).