| 摘要 |
PURPOSE:To reduce the cost of a power source by charging a secondary battery by electricity supplied from a telephone line and using the charged electricity stored in the secondary battery to activate electric circuits. CONSTITUTION:The secondary battery 9a of a 1st power supply section 9 is connected to a telephone line network L via, e.g., 1.1Mohm resistor 9b, and charged up by a current supplied from the network L at a rated voltage of 3.6V. A nickel and cadmium battery or the like is used for the battery 9a. Then the power to a line changeover relay 5 in the electric circuits 1, a reception circuit 6, a PB signal generating circuit 7, and a microprocessor 8 by the energy stored in the battery 9a. A primary battery control circuit 10b supplies power to the electric circuit 1 if the voltage of the battery 9a is lower than the voltage of the battery 10a.
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