Abstract: A system of the local area network (LAN) type using a closed loop optical fibre transmission medium, in which a series of stations, one of which acts as a master station, are connected to the loop. In each TDM cycle, a group of adjacent time slots is used as a framing group which occurs once per cycle of the system, the framing group including a multi-bit group number position which identifies a slot or group of slots. The loop includes a latency buffer to set the loop delay time to exactly 125 micro seconds, and the system according to the invention provides for both circuit-switched and packet-switched connections. To set up a circuit-switched connection, a free slot is chosen and its identity signaled in a packet manner. The proportion of slots allocated to circuit connections is varied dynamically, with indication thereof conveyed in a framing group of slots which occurs once in a cycle.

Abstract: A method of balancing digital signals encoded in the Miller Code, which is inherently an unbalanced code. Additional coding rules are utilized based on the use of a transition interval extending from the begining of a bit period to the begining of the next but one bit to define an adjacent pair of Binary I's for certain specific data sequences.

Abstract: A digital duplex transmission system for use in a local area uses a modified dipulse code from the exchange terminal to the subscriber terminal and either a different modified dipulse code or a modified AMI (Alternate Mark Inversion) code in the other direction to achieve time separation of signals at each terminal. Incorporation of a hybrid separator in each terminal further improves the performance of the system.