User`s guide

56K Professional Message Modem 71

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 Reserved

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 UK calls

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

5 32 Disables V.32

bis

mode

6 64 Disable V.42 selective reject