V.25
An ITU-Tstandard 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-Tstandard 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-Tstandard for facsimile operations that specifies modulation at 4800 bps, with fallback to 2400 bps.
V.29
An ITU-Tstandard for facsimile operations that specifies modulation at 9600 bps, with fallback to 7200 bps.
V.32
An ITU-Tstandard 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-Tstandard 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.
