Abstract: In a data transmission system of the TDM type both circuit-switched and packet-switched connections can be set up. Circuit-switched connections, being real time, e.g. voice, are given priority, but all time slots are available for packets when not in use for circuit-switched connections. Thus the ratio of the two types of connections is automatically adjusted according to traffic conditions.

Abstract: In a PCM system, it is desirable for the two ends to remain in synchronization, and for this purpose both channel associated and non-channel associated synchronizations are used.The PCM code combinations are eight bit codes, each with a ninth bit for sync and a tenth bit for data. When sync search is in progress, either at switch on or after sync has failed, the seventh and eighth bits of the PCM code bits are used to convey additional sync thus reducing the risk of simulation. To locate the sync, all other bits except the sixth and tenth bits are set to zero, the sixth and tenth bits being at one. Thus, two ones are separated by five zeros to form a pointer used to locate the sync pattern. The sync pattern is located by storing a data frame on reception and shifting it to find the combination of two ones separated by five zeros. The shift needed to find the combination indicates the extent of misalignment and is used to bring the receiver clock into alignment with the incoming bit streams.