User`s manual

U.S. Robotics I-modem Command Reference
Glossary • Page G-44
V.21 Fax
An ITU-T standard for facsimile operations at 300 bps. U.S. Robotics or compatible fax
devices then transmit or receive at higher speeds.
V.21
An ITU-T standard for modem communications at 300 bps. Modems made in the United
States or Canada follow the Bell 103 standard. However, the modem can be set to answer
V.21 calls from overseas.
V.22
A ITU-T standard for modem communications at 1200 bps, compatible with the Bell
212A standard observed in the United States and Canada.
V.22bis
An ITU-T standard for modem communications at 2400 bps. The standard includes an
automatic link negotiation fallback to 1200 bps and compatibility with Bell 212A/V.22
modems.