TDM telecommunications system - uses double ring connection for PCM transmission by involving synchronisation signals

摘要

The communications system consists of a number of subscriber stations connected by two ring connections to a central control station. Data are sent between stations in pulse-code-modulated form on a time-sharing basis. Each subscriber (3-8) is connected via an input/output interface (3a-8a) to two ring connections (2,9), which start and finish at the central station (1). - Each subscriber can take free time-slots on the primary ring (2) to send a call code, and if time is available and the required receiving station(s) is free, transmission can commence, with the aid of synchronisation signals from the central station. The secondary ring (9) operates in the reverse direction to the primary (2) and the central station uses it to detect changes in the system, such as ends of calls and faults.(1)