Hayes AT commands cheat sheet

The Hayes AT command set was how software talked to a modem: plain text starting with AT ("attention"). These are the commands our virtual modem understands. Try them in the console under the player.

Command	What it does here	Example
`ATDT`number	Dial with tones (DTMF) and play the call	`ATDT555-0199`
`ATDP`number	Dial with pulses: 10 clicks per second, 60/40 break/make	`ATDP4159`
`ATH`	Hang up	`ATH`
`ATM0` / `M1` / `M2`	Speaker off / on until carrier detect (default) / always on	`ATM2`
`ATL0`–`L3`	Speaker volume, quietest to loudest (default L2)	`ATL3`
`ATS11=`ms	DTMF tone and gap length, 50–255 ms (default 95); `ATS11?` reads it	`ATS11=60`
`AT+MS=`mode	Choose the modulation: `V92`, `V90`, `V34`, `V32B`, `V22B`, `B103`	`AT+MS=V34`
`ATX`n	Result-code detail: `X0` reports plain `CONNECT`, `X1`–`X4` add the speed and protocol	`ATX0`
`ATZ`	Reset to defaults	`ATZ`
`ATI`	Identify the modem	`ATI`

Commands can be chained: ATM2L3DT5550199 turns the speaker on for the whole call, at full volume, and dials.

Result codes

`OK`	Command accepted
`CONNECT 52000/V.90`	Carrier detected; the speed and standard follow (with X1 or higher)
`BUSY`	The line was engaged
`NO CARRIER`	Something answered but no modem connection formed, or the call was hung up
`NO ANSWER`	Ringing with no reply
`ERROR`	The command was not understood

Number Modem Country Line

Ready. Press Dial.

Speed 1.00× Volume -12 dB Speaker (ATM) Stereo split Loop phase Nerd detail

caller

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answerer

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AT console (Hayes commands)

Event list (the spectrogram as text)

The console and the controls mirror each other: change the modem menu and the console shows the AT+MS command it corresponds to. Real modems had hundreds more commands and S-registers, and the exact set varied by manufacturer. We support only the ones that change the sound. Hayes command syntax is a de facto standard, not an ITU recommendation; ITU-T V.250 later standardized much of it.