3Com U.S. Robotics 56K Voice User Manual page 74

Register Default
S19 0
S20 0
S21 10
S22 17
S23 19
S24 0
S25 20
S26 0
S27 0
68 56K Voice Faxmodem Internal - User's Guide
Technical Reference
Function
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.
Reserved
Sets the length, in 10-millisecond units, of breaks sent
from the modem to the computer; applies to MNP or
V.42 mode only.
Stores the ASCII decimal code for the XON character.
Stores the ASCII decimal code for the XOFF character.
Reserved
Sets the duration, in hundredths of a second, that DTR
must be dropped so that the modem does not 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.)
Reserved
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.