PURPOSE: To supply power stably to an adaptor of a terminal equipment such as a telephone set.
CONSTITUTION: A line power supply control circuit 1 is connected between terminals L1, L2 to which a telephone line is connected and terminals TL1, TL2 to which a terminal equipment such as a telephone set is connected. A series circuit comprising a 1st one-way conduction element circuit 11 of the control circuit 1 and a light emitting diode section 13 of a photocoupler is inserted to a line between the terminals L1 and TL1. The series circuit is connected between a base and an emitter of a transistor(TR) circuit 18 and its collector is connected to an input terminal of a power output circuit 3 via 1st and 2nd feeding lines 21, 22 of a feeding control circuit 2. The 1st feeding line 21 is made up of a light receiving element section of a photocoupler. An output terminal of the power output circuit 3 is connected to an adaptor 4 of a terminal equipment.
TAKAHASHI MASABUMI
HOSHI SATOSHI
SHIMADA IKUKO
NIPPON TELEGRAPH & TELEPHONE