Tdm fault detector

Claim 1

An automatic telecommunication exchange, in which communication connections are established in time division multiplex manner, said exchange including incoming and outgoing multiplex highways each accommodating n multiplex channels, a plurality of cross-exchange highways each of which can interconnect a number m of said incoming highways and a number m of said outgoing highways via static electrical switching devices, control means associated with said highways whereby the channels on m of said highways are interleaved for transmission over said cross-exchange highways, so that a said cross-exchange highway can handle m times as many connections as can an incoming or outgoing highway, timing means for defining a multiplex cycle in which each frame includes n time slots used for other than communication connections, and test means adapted to test said cross-exchange highways and said switching devices, said test means including controls causing the test means to be operable only during the time slots used for other than communication connections, so that said highways and said switching devices can be tested without interfering with the connections.