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Appendix C - AT commands
Standard AT Commands
Most modems use the standard AT commands, as shown in the following tables. Consult the
manual for your modem to set what AT commands it supports.
Note that the trailing "n" in many commands indicates a number.
The allowable numbers, and their effect, are listed below the command.
Command Description
<any key> Terminate current connection attempt
+++ Escape sequence code, entered in data state, wait for modem to return to
command state
ATA Force answer mode on-line
ATBn Handshake operation
B0 Select ITU-T V.22 for 1200 bps communication
B1 Select Bell 212A for 1200 bps communication
ATD Dial number and options that follow
P Pulse dial
T Tone dial
, Pause for a specified time
; Return to command state after dialing
! Hook flash, call transfer
W Wait for second dial tone
@ Wait for 5-second silence before proceeding, otherwise return O ANSWER"
R Reverse Dial (Originate a call in answer mode)
ATDL Dial last number
ATDSn Dial number stored in NVRAM at position n. (n=0..9)
ATEn Command mode local echo of keyboard commands
E0 Echo off
E1 Echo on
ATHn On/Off hook control
H Hang up modem
H0 Hang up (on hook), same as ATH
H1 Get off hook
ATIn Display inquired information
I0 Display product code
I1 Display product information and ROM checksum
I2 Link status report
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