3Com 56K manual Bit Result

A complete list of S-Registers A-9

Register	Default	Function
		Error control handshaking options: Select the total value
		of bits 4 and 5
		Bit 4	Bit 5	Result
		0	0	Complete handshaking sequence:
				V.42 Detection, LAPM error control,
				MNP.
		16	0	Disable MNP.
		0	32	Disable V.42 Detection and LAPM.
		16	32	Disable Detection phase, if you
				know that the remote Business
				Modem does LAPM, but not the
				Detection phase.
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	Value	Result
		0	1	Disable V.32bis. Used for
				troubleshooting; 3Com Technical
				Support may ask you to disable
				V.32bis for testing purposes.
		1	2	Disable the Business Modem's
				enhanced, proprietary V.32bis
				modulation. Used for
				troubleshooting.
		2	4	Disable the faster retrains that occur
				during proprietary V.32terbo
				modulation. Used for
				troubleshooting.
		3	8	Enable V.23. Required for some
				British connections.