| 摘要 |
PURPOSE:To bring a synthesizer tuner to the state of memory backup by using an output from a power supply circuit so as to allow an electronic input switching circuit to detect power failure and to generate a pulse and giving it to the synthesizer tuner. CONSTITUTION:Since an output at an output terminal 10 of a power supply circuit 3 is OV as soon as a power fault takes place, a voltage of an anode 20 of a diode 19 rises at a time constant comprising a resistor 15 and a capacitor 18. Since the time constant is set freely independently of the other circuit, the time constant is set to be sufficiently smaller and a half wave rectifier circuit whose voltage rises as soon as the power failure takes place is constituted practically. When the voltage of the anode 20 of the diode 19 rises, since a transistor 17 (TR) is turned on, a chip enable terminal 7 of the synthesizer tuner connected to the TR 17 goes to a low level and the synthesizer tuner 1 enters the memory backup operation.
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