3Com 56K For HST modulation only, From 1.5K bytes to 128.* for, Calls from remote users of slower

S-Registers I-3

Register	Default	Function
S15	0	Bit-mapped register. (See Chapter 1, Using the AT
		Command Set, for instructions about how to set
		bit-mapped registers.)

Bit	Value	Result
0	1	Disable the Business Modem's extra
		high-frequency equalization if it
		causes problems on shorter-link calls
		(for HST modulation only).
1	2	Disable online fallback.
2	4	Disable 450 bps back channel* HST
		only.
3	8	Reset non-ARQ mode Transmit buffer
		from 1.5K bytes to 128.* (for the
		convenience of BBS operators taking
		calls from remote users of slower
		modems).
4	16	Disable MNP Level 4; retransmitting
		the larger Level 4 data blocks may be
		a problem if you expect a great
		number of errors during a call.
5	32	Set Backspace key to delete.
6	64	Some earlier 2400 bps MNP modems,
		not made by 3Com, U.S. Robotics, or
		Microcom, were not fully compatible
		with the MNP protocol. If you have
		difficulty making a successful 2400
		bps MNP connection with a remote
		MNP modem, it may be because of
		this incompatibility. Set S15 to 64 and
		try again to make the connection.
7	128	Custom applications only.
		* The default 1.5K byte non-ARQ
		buffer allows data transfer with X-

and Y-modem-type File Transfer Protocols without using flow control.

The 128-byte option allows remote users with slower modems to stop your transmitted data from scrolling off their screens. When remote users send your computer an XOFF (<Ctrl-S>) and you stop transmitting, the data in transit doesn’t exceed the size of their screen.