A Time Divison Multiplex Ring (TDM Ring) comprising a plurality of nodes (central offices) connected together by interchange trunks (main and standby paths) in a ring type configuration. Each node contains a multiplexer, a demultiplexer, data, alarm, bridging, switching circuits, transmitters and receivers...http://www.google.fr/patents/US4633246?utm_source=gb-gplus-shareBrevet US4633246 - Time divison multiplex ring
