Fault location circuit for duplex digital transmission installation - enables terminal to evaluate distance to faulty repeater by timing propagation of test signal around loop

摘要

A generator (10) at the terminal (A or B) transmits a test signal (P) repeatedly and without interruption on the line (2 or 2') to the other terminal. At each regenerative repeater station (11) in full working order a circuit (5) recognises this signal and makes a loop-back connection. The test signal is returned on the other line (2' or 2) and the loop is broken, except at the last intact repeater which receives no loop-back from its faulty neighbour. At the terminal a timing circuit (23) works out the position of the fault from measurement of the test signal propagation time and knowledge of propagation velocity. USEADVANTAGE - Mobile digital communications. All repeaters are of identical construction and any defective station can be located easily from either end terminal.