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Modem ATCommands and S-Registers B-1
Appendix B
Modem AT Commands and
S-Registers
The AT command set allows you to control your modem from a command line
or from terminal mode. Some guidelines for using the AT command set are
listed in the following tables.
• AT commands are usually preceded by AT. They are not case sensitive
and do not require spaces in the command strings themselves.
• AT commands can be invoked from any modem communications software
under terminal mode.
• AT commands invoked normally get a response of OK, ERROR or other
messages, depending on the command. These are sometimes called
"result codes".
•A Y in the Default column indicates that the command is preset at the
factory. You can set the defaults by entering AT&F.
• An N appearing in the command string indicates that a number needs to
replace it.
• AT commands can be invoked from any communications software under
terminal mode.
Table B.1 AT Command Summary
Command Description Usage Default
A/ Re-execute last
command
Allows last successful command
entered to be re-executed
N
ATA Respond to call
Allows manual response when
call is received from another
modem. The S0=1 command
sets the modem to answer
automatically.
N
ATB0
Select V.22 at 1200
bps
Select V.22 connection at 1200
bps
Y
ATB1 Bell 212A at 1200bps
Select Bell 212A connection at
1200 bps
N
ATC1 Response message Return OK message N
ATD Dial Command Get the modem to dial N
ATDn Dial modifier Dial modifier N
ATE0 Local Echo Off
Do not display the characters you
type
N
ATE1 Local Echo On
Display the characters when you
type
Y
(continued through page B-6)