| 摘要 |
PURPOSE:To use a telephone function even at the time of power failure by using a light beam outputted from a light emitting element to be turned on/off by a DC voltage impressed to a telephone circuit to control a selecting signal generating means. CONSTITUTION:When an operator unhooks a handset 3b to telephone, telephone circuits L1, L2 are connected in series through a hook switch 3f, a DC closing circuit 3e, a switch 5, a resistor 6, and light emitting diodes 7, 8 and a DC circuit consisting of the telephone circuits L1, L2 is held. When the light emitting diodes 7, 8 are turned on, a vol-gate is generated from a photovoltaic diode array 20 for detecting the light beams outputted from the diodes 7, 8 and supplied to a selecting signal generating circuit 24 and a CPU 25. Consequently, the circuit 24 and the CPU 25 are turned to operatable state.
|
