3Com 56k User's Manual And Reference page 67

Register Default
S7 60
S8 2
S9 6
S10 14
S11 72
S12 50
S13 0
Technical Reference
Function
Sets the number of seconds the modem waits for a carrier
Sets the duration, in seconds, for the pause (,) option in the Dial command
Sets the required duration, in tenths of a second, of the remote modem's carrier signal before
recognition by the modem
Sets the duration, in tenths of a second, that the modem waits to hang up after loss of carrier.
This guard time allows the modem to distinguish between a line disturbance from a true
disconnect (hang up) by the remote modem.
Note: If you set S10 = 255, the modem will not hang up when carrier is lost
Dropping DTR hangs up the modem
Sets the duration and spacing, in milliseconds, for tone dialling
Sets the duration, in fiftieths of a second, of the guard time for the escape code sequence (+++)
Bit-mapped register
Select the bit(s) you want on and set S13 to the total of the values in the Value column
For example: ATS13 = 17 enables bit 0 (value is 1) and bit 4 (value is 16)
Bit Value Result
0 1 Reset when DTR drops
1 2 Reset non-MNP transmit buffer from 1.5K to 128 bytes*
2 4 Set backspace key to delete
3 8 On DTR signal, autodial the number stored at position 0
4 16 At power on/reset, autodial the number stored at position 0
63