User`s guide

56K Professional Message Modem 49
V.29
This is the
ITU-T
standard for
facsimile
operations that specifies
modulation at 9600 bps, with fallback to 7200 bps.
V.32
This is the
ITU-T
standard for modem communications at 9600 bps and
4800 bps. V.32 modems fall back to 4800 bps when line quality is
impaired.
V.32 bis
This is the
ITU-T
standard that extends the V.32 connection range:
4800, 7200, 9600, 12,000, and 14,400 bps. V.32
bis
modems fall back to
the next lower speed when line quality is impaired, fall back further as
necessary, and also fall forward (switch back up) when line conditions
improve.
See
online fall back/fall forward
.
V.34
An
ITU-T
standard that currently allows data rates as high as 33,600bps
and 28,800 bps.
V.34+
This is an enhancement to
V.34
that enables data transfer rates as high
as 33,600 bps.
V.90
An
ITU-T
standard that currently allows data rates as high as 56,000 bps
receive and 31,200 bps transmit.
x2™
A 3Com proprietary protocol that allows data rates as high as 56,000
bps receive and 31,200 bps transmit.
V.42
This is the
ITU-T
standard for modem communications that defines a
two-stage process of detection and negotiation for
LAPM error control
.
V.42bis
The is an extension of
ITU-T
V.42 that defines a specific data
compression scheme for use during V.42 connections.