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CHAPTER 5: Commands
Register
Default
Function
S19
0 (zero)
Sets the duration, in minutes, for the inactivity
timer. The timer activates when there is no
data activity on the phone line; at time-out the
modem hangs up. S19 = 0 disables the timer.
S20
0 (zero)
Reserved.
S21
10
Sets the length, in 10-millisecond units, of
breaks sent from the modem to the computer;
applies to MNP or V.42 mode only.
S22
17
Stores the ASCII decimal code for the XON
character.
S23
19
Stores the ASCII decimal code for the XOFF
character.
S24
0 (zero)
Reserved.
S25
20
Sets the duration, in hundreths of a second,
that DTR must be dropped so that the modem
doesn’t interpret a random glitch as a DTR
loss. (Most users will want to use the default;
this register is useful for setting compatibility
with older systems running under older
operating software.)
S26
0 (zero)
Reserved.
S27
0 (zero)
Bit-mapped register setup. To set the register,
see instructions for S13.
Bit
Value
Result
0 (zero)
1
Enables ITU-TSS V.21
modulation at 300 bps for
overseas calls; in V.21
mode, the modem answers
both overseas and domestic
(U.S. and Canada) calls.
