Digital data transmission system - combines signalling and message signals with quasi-random sequence but leaves sync. signals unchanged

摘要

The transmission system connects a digital telephone exchange to a digital subscriber station via a two-wire line. Data signal groups are constructed comprising signalling, message, and sync. signals. The bits representing signalling signals and at least one message signal word in the message signal block are combined with a quasi-random sequence of bits for the time they are transmitted over the line. The synchronisation bits on the other hand are sent unchanged. At the receiver, the reverse process is performed and the quasi-random sequence removed to retrieve the original signalling and message signals.