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Scope

This International Standard specifies elements of data link control procedures for synchronous or start/stop, code- transparent data transmission using the HDLC frame structure specified in ISO/IEC 3309 and independent frame numbering in both directions.

These HDLC elements of procedures are defined specifically in terms of the actions that occur on receipt of commands at a secondary station or a combined station.

This International Standard is intended to cover a wide range of applications; for example one-way, two-way alternate or two- simultaneous data communication between data stations which are usua lly buffered, including operations on different types of data circuits; for example multipoint/point-to-point, duplex/half-duplex, switched/non-switched, synchronous/start-stop, etc.

The defined HDLC elements of procedures are to be considered as a common basis for establishing different types of control procedures. This International Standard does not define any single system and should not be regarded as a specification for a data communication system. Not all of the commands or responses are required for a particular system implementation.