T
ECHNICAL
Q
UICK
R
EFERENCE
129
Register Default
Function
S25
20
Sets the duration, in hundredths 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
Reserved
S27
0
Bit-mapped register setup. To set the register, see instructions for S13.
Bit
Value
Result
0
1
Enables ITU-T 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,
but only originates V.21 calls. (Default Bell 103)
1
2
Enables unencoded (non-trellis coded) modulation in
V.32 mode.
2
4
Disables V.32 modulation.
3
8
Disables 2100 Hz answer tone to allow two V.42
modems to connect faster.
4
16
Enables V.23 fallback mode.