Western Telematic Data/FaxModem manual Default Function

					S-Registers
Register	Default	Function
S10		Although it is not recommended to connect to a line
(continued)		with call waiting, the S10 register can be adjusted
		upward to prevent the modem from misinterpreting
		the second call signal as a remote disconnect. If call
		waiting is a problem, it is preferable to contact your
		phone company to determine the command to
		temporarily disable call waiting (typically *70W).
		For example: ATDT *70W phone number.
		Note: If S10 = 255, the modem will not hang up
		when the carrier is lost. Dropping DTR hangs up the
		modem.
S11	70	Sets the duration and spacing (in milliseconds) for
		tone dialing.
S12	50	Sets the duration (in fiftieths of a second) of the guard
		time for the escape code sequence (+++).
S13	0	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 in NVRAM at
				position 0.
		4	16	At Power On/Reset, autodial the
				number stored in NVRAM at
				position 0.
		5	32	Reserved
		6	64	Reserved
		7	128	Disconnect on escape code.

*The 1.5K-byte non-ARQ buffer allows data transfer with Xmodem and Ymodem type file transfer protocols without using flow control.

The 128 Byte option allows remote users with slower modems to prevent transmitted data from scrolling off screen. When a remote user sends an XOFF (Ctrl-S) to your computer and transmission stops, data in transit from your modem's buffer does not exceed the size of the remote user's screen. This is also helpful when a remote modem/printer application is losing characters.

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