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 | |
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+++ |
| Escape sequence code, entered in data state, wait for modem to return to |
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ATA | Force answer mode | |
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ATBn | Handshake operation | |
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| B0 | Select |
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| B1 | Select Bell 212A for 1200 bps communication |
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ATD | Dial number and options that follow | |
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| P | Pulse dial |
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| T | Tone dial |
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| , | Pause for a specified time |
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| ; | Return to command state after dialing |
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| ! | Hook flash, call transfer |
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| W | Wait for second dial tone |
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| @ | Wait for |
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| R | Reverse Dial (Originate a call in answer mode) |
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ATDL | Dial last number | |
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ATDSn | Dial number stored in NVRAM at position n. (n=0..9) | |
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ATEn | Command mode local echo of keyboard commands | |
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| E0 | Echo off |
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| E1 | Echo on |
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ATHn | On/Off hook control | |
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| H | Hang up modem |
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| H0 | Hang up (on hook), same as ATH |
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| H1 | Get off hook |
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ATIn | Display inquired information | |
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| I0 | Display product code |
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| I1 | Display product information and ROM checksum |
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| I2 | Link status report |
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