AT commands
The Hayes Smartmodem command set include the AT command set used by many popular modems.
This information comes from the Hayes Smartmodem 2400 Quick Reference Card, published by Hayes Microcomputer Products, Inc. Consult the modem documentation for a list of relevant AT commands.
| Item | Description |
|---|---|
| AT | Command prefix - precedes command line. |
| <CR> | Carriage return (newline) character - terminated the command line. |
| A | Go off-hook, remain in command mode. |
| A/ | Repeat previous command line. This command is not preceded with AT or followed by <CR>/. |
| B0 | Select CCITT V.22 standard for 1200 bps communications. |
| B1 | Select Bell 212A standard for 1200 bps communications. |
| D | Enter originate mode, dial the number that follows, and attempt to go online. D is usually followed by T for tone, P for pulse may also be used. |
| DS=n | Dial the number stored in location n |
| E0 | Disable character echo in the command state. |
| E1 | Enable character echo in the command state. |
| H0 | Go on-hook (hang up the phone). |
| H1 | Operate switch-hook and auxiliary relay. |
| I0 | Return product identification code. |
| I1 | Perform checksum on firmware ROM; return checksum. |
| I2 | Perform checksum on firmware ROM; returns OK or ERROR as
the result. |
| L0 | Speaker off. |
| L1 | Low speaker volume. |
| L2 | Medium speaker volume. |
| L3 | High speaker volume. |
| M0 | Speaker off. |
| M1 | Speaker on until carrier detected. |
| M2 | Speaker always on. |
| M3 | Speaker on until carrier detected, except during dialing. |
| O0 | Enter online state. |
| O1 | Enter online state and initiate equalizer retrain. |
| Q0 | Modem returns result codes. |
| Q1 | Modem does not return result codes. |
| Sr | Set pointer to register r. |
| Sr=n | Set register r to value n. |
| V0 | Display result codes in numeric form. |
| V1 | Display result codes in verbose form (as words). |
| X0 | Enable features represented by result codes 0-4. |
| X1 | Enable features represented by result codes 0-5, 10. |
| X2 | Enable features represented by result codes 0-6, 10. |
| X3 | Enable features represented by result codes 0-5, 7, 10. |
| X4 | Enable features represented by result codes 0-7, 10. |
| Y0 | Disable long space disconnect. |
| Y1 | Enable long space disconnect. |
| Z | Reset modem |
| &C0 | Assume data carrier always present. |
| &C1 | Track presence of data carrier. |
| &D0 | Ignore DTR signal. |
| &D1 | Assume command state when an on-to-off transition of DTR occurs. |
| &D2 | Hang up and assume command state when an on-to-off transition of DTR occurs. |
| &D3 | Reset when an on-to-off transition of DTR occurs. |
| &F | Recall the factory settings as the active configuration. |
| &G0 | No guard tone. |
| &G1 | 500 Hz guard tone. |
| &G2 | 1800 Hz guard tone. |
| &J0 | RJ-11/RJ41/RJ45S telco jack. |
| &J1 | RJ-11/RJ-13 telco jack. |
| &P0 | Pulse dial with make/break ratio 39/61. |
| &P1 | Pulse dial with make/break ratio 33/67. |
| &Q0 | Operate in asynchronous mode. |
| &Qn | Operate in synchronous mode n |
| &R0 | Track CTS according to RTS. |
| &R1 | Ignore RTS; always assume presence of CTS. |
| &S0 | Assume presence of DSR signal. |
| &S1 | Track presence of DSR signal. |
| &T0 | Terminate test in progress. |
| &T1 | Initiate local analog loopback. |
| &T3 | Initiate digital loopback. |
| &T4 | Grant request from remote modem for remote data link (RDL). |
| &T5 | Deny request from remote modem for RDL. |
| &T6 | Initiate remote digital loopback. |
| &T7 | Initiate remote digital loopback with self-test. |
| &T8 | Initiate local analog loopback with self-test. |
| &V | View active configuration, user profiles, and stored numbers. |
| &Wn | Save storable parameters of active configuration as user profile n. |
| &X0 | Modem provides transmit clock signal. |
| &X1 | Data terminal provides transmit clock signal. |
| &X2 | Receive carrier provides transmit clock signal. |
| &Yn | Recall user profile n. |
| &Zn=x | Store phone number x in location n. |