V32bis

V32bis, often written as V.32bis, is a data communication standard in the ITU-T V-series developed as an enhanced revision of V.32 for dial-up modems. It enables full-duplex data transmission over analog telephone lines at up to 9600 bit/s, with backward compatibility to V.32 networks and equipment.

Implementation and operation: The standard defines modulation schemes, signal levels, timing, handshaking, and error-control procedures that allow modems to establish connections and negotiate data rate and line parameters. V32bis is commonly implemented in PC modems through an AT command interface, enabling hosts to establish and manage connections.

History and impact: Introduced in the late 1980s as an improvement over V.32, it saw widespread deployment through the 1990s in consumer and business modems. It offered better throughput and reliability on noisy telephone lines, aiding services such as text-based bulletin board systems and early online services. It gradually declined with the advent of faster standards such as V.34 and V.90 in the late 1990s.

Variants and compatibility: V32bis is designed to be backward compatible with V.32; some devices supported both to ease interoperability.

See also: V.32, ITU-T V-series, V.34, V.90.