User`s manual

U.S. Robotics I-modem Command Reference
Glossary • Page G-45
V.23
An ITU-T standard for modem communications at 1200 bps with a 75 bps back channel.
Used in the U.K.
V.25
An ITU-T standard for modem communications. Among other things, V.25 speciÞes an
answer tone different from the Bell answer tone. All U.S. Robotics modems can be set
with the B0 command so that they use the V.25 2100 Hz tone when answering overseas
calls.
V.25bis
An ITU-T standard for synchronous communications between the mainframe or host and
the modem using the HDLC or character-oriented protocol
. Modulation depends on the
serial port rate and setting of the transmitting clock source, &X.
V.27ter
An ITU-T standard for facsimile operations that speciÞes modulation at 4800 bps, with
fallback to 2400 bps.