A METHOD OF DETECTING THE PRESENCE OF LOAD COILS ON SUBSCRIBERS LOOPS, BY THE USE OF TRANS-HYBRID LOSS MEASUREMENTS

摘要

A method for determining whether a subscriber loop has load coils comprises applying test tones in the voice band to a hybrid circuit terminating the subscriber loop at the transmitter pair of the four-wire side of the circuit. Reflections are measured at the receiver pair of the four-wire side of the hybrid circuit. If the amplitude of the reflections as a function of frequency decrease monotonically, the subscriber loop is declared to be free of load coils.