A Digital Loop Communication System

In this concise paper, we describe the concept of a local loop communication system with distributed control. Digital signals offered by the subscribers are parceled and transmitted in blocks to their destination using address-coding. Access of the terminals to the loop is gained by switching a delay network (shift register, containing the message block to be transmitted) into the loop line. This strategy guarantees that every station is able to transmit a message at any time regardless of the traffic conditions in the loop. A quantitative analysis of the loop traffic capabilities as a fnnction of the loop parameters is given. A laboratory model for line frequencies of about 10 Mb/s is presently being built. It allows data and telephone connections including such features as call back, call transfer and forwarding. Loop transmission is realized by means of a three-core symmetrical cable which carries the data sequences and the timing information separately. This allows the use of an extremely simple regenerator. Possible applications include integrated in-house communication systems and control and supervisory systems for manufacturing processes, railway stations and trains.