Digital communication system allowing time division multiplexing - sends fault alarm via all other exchange-interconnecting cables if cable fails from first exchange drawing clock signal from this cable

摘要

After the failure of a clock signal delivering interconnect to an exchange, the next connected exchange sends on its own clock signal as well as a signal denoting the failure to all connecting lines. Clock priorities are compared at the following exchanges before establishing the new system synchronisation. One exchange can store the clock priority of the exchange delivering the clock signal serving as master priority. USE - Allows system to handle line breakdown, installation and priorities electrically.