Automatic fault location in telephone exchange - by interrogating circuits for state and designating as faulty those in which no engaged signal is stored

摘要

The telephone consists of one central and several decentral units. When a circuit is engaged, states of all the other circuits of the same type are interrogated. Signals representing their engaged or free state are stored in a memory whose content is interrogated within time intervals determined by different operational demands. Circuits in which no engaged signal is stored within such a time interval are designated and signalled as faulty.