Synchronisation fault location in PCM telephone exchange - reports diagnosis of line or exchange fault to controller using resetting loop

摘要

Loss of block synchronisation by a connection unit of a time-multiplex PCM telephone exchange, initiates an automatic routine to diagnose the fault location. First the output is looped back to the input, and the synchroniser is reset and the units sends all 'ls' as a fault signal. If synchronisation is still lost, the connection unit is faulty. This fact is reported to and stored by the exchange controller. If synchronisation is recovered, the fault is incoming. A unit receiving a fault signal proceeds to check itself. If the test fails it reports itself faulty to the exchange controller, if not, it reports the line faulty.