Specifications
August 26, 2004 TechMemo 01-0011B
16 of 24
AT commands
The AT commands used in this section only apply to US Robotics 56K V.90 and V.92 Faxmodems.
Though some of the AT commands used below might work with other modems, consult your modem’s
documentation for a list of AT commands specific to your modem.
NOTE: Modem default settings are in italics.
Command Function
BASIC COMMANDS
$ Used with D, S, or & commands (or just AT) to display a basic command list.
A Manual answer — goes off hook in answer mode. Pressing any key before a connection stops the operation.
A/ Re-executes the last command. Used mainly to redial. Does not require the AT prefix or a carriage return.
A>
Re-executes the last command continuously until a user intervenes. Otherwise, the command will execute forever. Does
not require the AT prefix or a carriage return.
+++ Escapes to online-command mode.
AT Required prefix for most modem commands except A/, +++, and A>. Use AT alone to test for OK result code.
Bn
US/ITU-T answer sequence:
• B0 — ITU-T answer sequence.
• B1 — US answer tone.
Dn
Dials the specified phone number (for example, ATDT9,5551212). Includes the following:
• 0 - 9 — numeric digits.
• # , * — extended touch-pad tones.
• L — dials the last number dialed.
• P — pulse (rotary) dial.
• R — originates call using answer (reverse) frequencies.
• Sn — dials the phone number string stored in NVRAM at position n. Phone numbers are stored with the &Zn=s
command.
• T — tone dial.
• ,(comma) — pause. Linked to S8 register.
• ; (semicolon) — return to command mode after dialing.
• “ (quotes) — dials the letters that follow (in an alphabetical phone number).
• ! (exclamation point) — flashes the switch hook.
• / (backslash) — delays for 125 ms before proceeding with dial string.
• W — wait for second dial tone (X2 or X4). Linked to S6 register.
• @ — dials, waits for quiet answer, and continues (X3 or higher).
• $ — displays a list of dial commands.
En
Sets command mode echo (also controlled by DIP switch #4):
• E0 — echo off. Your typing will not appear on the screen.
• E1 — modem displays keyboard commands. Your typing will appear on the screen.
Fn
Sets online local echo — if on, a modem displays on your screen the data it is transmitting to another modem:
• F0 — online echo on. (Sometimes called half duplex.)
• F1 — online echo off. (Sometimes called full duplex.)
Hn
Goes on/off hook:
• H0 — hangs up (goes on hook)
• H1 — picks up (goes off hook).