| 摘要 |
PURPOSE:To make it possible to select automatically a channel where the broadcast signal exists, by performing channel successive advance when no broadcast signal exists at a main current supply time. CONSTITUTION:Power source circuit 4 supplies the power source voltage of pulse oscillating circuit 5 from 200msec after main power supply up to 1 sec by transistors 9 and 10 and limits the operating time of pulse oscillating circuit 5. By supply of the power source voltage, pulse oscillating circuit 5 supplies positive-polarity pulses of a period of approximately 10msec to transistor 17 to give channel successive advance pulses to input terminal 8 of channel selection IC. When detecting the broadcast signal, receiving detecting circuit 6 stops oscillation of oscillating circuit 5 to stop supply of the channel successive advance signal. |
