Data communication system and apparatus.

摘要

A network providing communication between end units (1). Each end unit (1) receives an entitlementto transmit in the form of a go-ahead. It is then able to transmit a frame of user data, which is broadcast by a central unit (7) to all other end units (1). When the end unit (1) transmitting the frame wishes to relinquish its entitlement, it transmits the go-ahead to the central unit (7) which passes it to the next end unit (1) taking them in a predetermined cyclic sequence. The system allows frames to be acknowledged: the central unit (7) collects acknowledgements from end units (1) receiving the frame successfully, and, when every expected station has acknowledged, returns an acknowledgement to the source end unit (1). Central units (1) may be combined to form largersystems.