S-Registers

Table B.4. S Registers

RegisterRangeDefaultFunction
S00-255 rings1-2Answer on ring number. Don't answer if 0
S10-255 rings0if S0 is greater than 0 this register counts the incoming rings.
S20-127 ASCII43 +Escape to command mode character
S2>127 no ESC
S30-127 ASCII13 CRCarriage return character
S40-127 ASCII10 LFLine feed character
S50-32, 127 ASCII8 BSBackspace character
S62-255 seconds2Dial tone wait time (blind dialing, see Xn)
S71-255 seconds30-60Wait time for remote carrier
S80-255 seconds2Comma pause time used in dialing
S91-255 1/10ths second6Carrier detect time required for recognition
S101-255 1/10ths second7-14Time between loss of carrier and hangup
S1150-255 milliseconds70-95Duration and spacing of tones when tone dialing
S120-255 1/50th seconds50Guard time for pause around +++ command sequence
S36

Fallback options when error correction link fails:

  • 0 - Disconnect

  • 1 - Establish Direct Connection

  • 3 - Establish Normal Connection

  • 4 - Establish an MNP connection if possible, else disconnect

  • 5 - Establish an MNP connection if possible, else Direct Connection.

  • 7 - Establish an MNP connection if possible, else Normal connection

7Negotiation Failure Treatment
S37
  • 1 = 300 bps

  • 5 = 1200 bps

  • 6 = 2400 bps

  • 7 = 1200/75 bps (v.23 mode)

  • 8 = 4800 bps

  • 9 = 9600 bps

  • 10 = 12000 bps

  • 11 = 14400 bps

  • 12 = 7200 bps

0Negotiation Speed (Initial handshake)

Many modems have dozens, even hundreds, of S registers, but only the first dozen or so are fairly standard. They are changed with a command like ATSn=N, and examined with ATSn? (e.g. AT S10=70 S1? would tell the modem not to hang up for seven seconds should it not hear the answering modem, and return the number of times the phone last rang.)