Toshiba V.90 - Manual (Page 73)

MNP and V.42
Flow control
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Commands (\ Nn )
The following N modulation handshake commands are used to set
the communication mode:
For details, refer to “AT Commands” on page 13 .
Flow control
In both normal mode and reliable mode, the buffers in the modem
and its flow control function permit communication even if the
speed is different between a personal computer and modem (serial
port) or between modems (modem port).
If there is a speed difference between the serial port and modem
port, the buffers in the modem will become full periodically.
Therefore, the communication activity is controlled so that data
transmission or reception is temporarily halted before the data
exceeds buffer capacity, and transmission is resumed when the
receiving buffers have room. This is the flow control function.
\N0, \N1 Remote modem unable to use MNP or V.42
\N2 Remote modem uses MNP
\N3 Uncertain if remote modem can use MNP or
V.42
\N4 Remote modem uses V.42
\N5, \N7 Same as \N3