3Com 56K Command Reference Manual page 145

Register Default Function
Error control handshaking options: Select the total value
of bits 4 and 5
Bit 4
0
16
0
16
S28 8 Sets the duration in tenths of a second of the extra
3000/600 Hz answer tones sent during V.32 hand-shaking.
This gives V.32 modems additional time to connect in V.32
mode before timing out.
If there is difficulty answering older, manually operated
V.32 modems (for example, modems that require a button
to be pushed in order to dial, try lengthening the duration
of the extra tones).Setting S28 to zero eliminates the extra
tones resulting in a faster connect time if, for example, the
Business Modem is set to use V.21 modulation (300 bps) or
V.23 modulation (1200 bps).
S29 20 Sets the duration, in tenths of a second, of the V.21 answer
tone.
S34 0 Bit-mapped register. See the beginning of this appendix for
information about setting bit-mapped registers.
Bit
0
1
2
3
A complete list of S-Registers
Bit 5 Result
0 Complete handshaking sequence:
V.42 Detection, LAPM error control,
MNP.
0 Disable MNP.
32 Disable V.42 Detection and LAPM.
32 Disable Detection phase, if you
know that the remote Business
Modem does LAPM, but not the
Detection phase.
Value Result
1 Disable V.32bis. Used for
troubleshooting; 3Com Technical
Support may ask you to disable
V.32bis for testing purposes.
2 Disable the Business Modem's
enhanced, proprietary V.32bis
modulation. Used for
troubleshooting.
4 Disable the faster retrains that occur
during proprietary V.32terbo
modulation. Used for
troubleshooting.
8 Enable V.23. Required for some
British connections.
A-9