Local area communication system for integrated services based on a token-ring transmission medium

摘要

In a local area communication system comprising token rings (11) with synchronous bandwidth managers SBM (15) for issuing priority tokens for quasi-synchronous frames at regular intervals, the rings are interconnected by a time division muliplex PBX unit (31, 33) via their SBM units. Buffers are provided in each SBM for synchron­ous information blocks transferred from and to the ring, and the TDM control (31) can independently access these buffers for TDM switching of the individual bytes of said information blocks. Besides this PBK interconnection for synchronous information or voice, the rings are also interconnected by a backbone bus or ring for transfer of asynchronous data between rings. A special slot re­arrangement procedure is provided to improve the filling of time slots in the quasi-synchronous frames that are no longer used after release of a connection, to allow for addapting the frame length (number of issued slots) to the number of existing connections.