CIRCUIT AND METHOD FOR DETECTING OPENING FOR DIGITAL SUBSCRIBER CIRCUIT HANDLED BY LOCAL FEED

摘要

PROBLEM TO BE SOLVED: To detect opening with stable operation without increasing power consumption. SOLUTION: A saturated voltage between the emitter and collector of a transistor 8 is made smaller than the sum of a cutoff voltage between the emitter and base of a transistor 3 and the forward voltage of a diode 6, when a current flowing to the transistor 8 is decreased, a current flowing to the collector side of the transistor 3 is detected by photodiodes 4-1 and 4-2 of a photocoupler and opening detecting signals are outputted from opening detecting signal sending terminals 11-1 and 11-2.