Terminal equipment for a secure bidirectional communication link carrying data multiplexed according to the synchronous digital hierarchy

摘要

The terminal includes two transmitter sections (TA1,TB1), with each removing an indication (FERF1',FERF2') of the digital word sequence end from a multiplexed SDH signal. Two multiplexed signals (D1a,D2a) are received and multiplexed with service words to form a secure connection and the two sequence end signals plus two further supplementary sequence signals (FERF3', FERF4') are added. The words are then transmitted on a single line (L1). A switch (SW1) allows transmission on the first line one of the two multiplexed signals from the transmission units.