V.25bis - technical definition

An ITU standard (1968) for automatic calling and/or answering equipment on dial-up lines. It has three modes: asynchronous (rarely used), character-oriented synchronous (bisync) and bit-oriented synchronous (HDLC/SDLC). Both synchronous versions are used in IBM AS/400 and other small-to-medium sized computers that do automatic dialing for remote job entry.

Due to the popularity of the Hayes AT Command Set, V.25bis is not used as widely in North America. It does not perform modem configuration functions and is limited to dialing and answering calls.