USRobotics V.34 - Manual (Page 223)

COURIER HIGH SPEED MODEMS
J-14 Glossary
V.25
An ITU-T standard for modem communications. Among other
things, V.25 specifies 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 answer-
ing overseas calls.
V.25 bis
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.27 ter
An ITU-T standard for facsimile operations that specifies
modulation at 4800 bps, with fallback to 2400 bps.
V.29
An ITU-T standard for facsimile operations that specifies
modulation at 9600 bps, with fallback to 7200 bps.
V.32
An 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, and fall forward again to 9600 bps when
line quality improves.
V.32 bis
An ITU-T standard that extends the V.32 connection range:
4800, 7200, 9600, 12K and 14.4K bps. V.32
bis modems fall back
to the next lower speed when line quality is impaired, and fall
back further as necessary. They fall forward to the next higher
speed when line quality improves.
V.32 terbo
Modulation scheme that extends the V.32 connection range:
4800, 7200, 9600, 12K, 14.4K, 16.8K, 19.2K, and 21.6K bps. V.32
terbo modems fall back to the next lower speed when line
quality is impaired, and fall back further as necessary. They fall
forward to the next higher speed when line quality improves.