Abstract: Synchronization of a receiving termination of a telecommunications system with an incoming data stream is carried out from a synchronization signal carried with the data stream. It is possible that a "mimic" of the synchronization signal may occur within the data stream. Two frame alignment detectors operate in worker/standby relationship, one being locked to a detected synchronization signal and the second searching for an alternative signal. Verification is carried out using a cyclic redundancy check.

Abstract: In modern digital telecommunications switching networks the switch block may be a duplicated plane time-space-time arrangement in which each time switch stage and each space switch stage is controlled by control stores. Each control store is cross-office slot ordered and is arranged to be loaded by the central control with the identity of the connection required for the relevant cross-office slot. At each busy cross-office slot in a time switch control store a 12 bit address word is retrieved. Ten bits are used to define the connection while the two remaining bits act as a busy bit and a parity bit. Each space switch control store contains in cross-office slot order eight bit address words (6 bits address plus busy and parity bits). The busy bits are used when interrogating the trunking for free paths and they are also used to control the application of idle codes to free slots in the speech path. The parity bits within the control stores are used to initiate pattern insertion on the speech highways.