Definitions for "X.21"
Keywords:  ccitt, itu, synchronous, dte, dce
In data communications, a specification of the CCITT that defines the connection of data terminal equipment to an X.21 (public data) network.
An ITU standard governing the serial interface between DCE and DTE, generally synchronous data on a DB15. Includes connector, electrical, and dialing specifications
A CCITT recommendation which specifies a general purpose interface between data circuit-terminating equipment for synchronous operation on public data networks.
International standard for very fast digital links. Supported in some PTT services (e.g., BT Kilostream in the UK).