IBM Aptiva Handbook page 173

Table 14: Common modem commands
Code/Command Function
Bn Sets the ITU-T or Bell communication standard:
n=0 Selects ITU-T V.22 mode when the modem is at 1200 bits per second (bps).
n=1 Selects Bell 212A when the modem is at 1200 bps (default).
n=2 Unselects V23 reverse channel (same as B3).
n=3 Unselects V23 reverse channel (same as B2).
n=15 Selects V.21 when the modem is at 300 bps.
n=16 Selects Bell 103J when the modem is at 300 bps (default).
C1 Sets normal transmit carrier switching.
Dsn The modem automatically dials a telephone number "n" where "n" is a complete telephone number. The command may
also include the following codes:
s=L Redials last number.
s=P Sets dialing to pulse dialing.
s=T Sets dialing to touch-tone dialing.
s=V Switches modem to speakerphone mode.*
s=W Waits for dial tone.
s=, Pauses while dialing.
s=@ Waits for quiet answer (5 seconds of silence).
s=; Returns the modem to command state after dialing.
s=! Causes the modem to go on-hook for 0.5 seconds and then go off-hook.
s=^ Disables data tone calling transmission.
* The DVn command is not supported by the TSR program that is required for operating the modem in DOS mode.
Ds=n Dials one of four telephone numbers previously stored using the &Zn=x command. The range of n is 0-3. See the Dsn
command for valid values for s.
En Sets Echo on or off. With echo on, the characters entered at your keyboard are displayed on your monitor.
n=0 Echo off
n=1 Echo on
F1 Disables online data character echo from the DTE.
Modem commands 157