Fault locating apparatus for digital transmission system

摘要

Defective repeaters in a multihop, digital microwave transmission system are located by the use of a special test pattern which is generated at the transmitting terminal. At each repeater station, the two outputs of the phase demodulator are compared to determine if the test pattern has been properly received from the upstream repeaters. The special test pattern, S, has the characteristic that S = S(2N); that is to say, the test pattern equals the complement of itself delayed by 2N symbols. This special characteristic makes it unnecessary to employ a differential decoder in the test apparatus at each repeater station.