| 摘要 |
PURPOSE:To prevent the wasteful electric power consumption due to the forgetting of the turning-off of an electric power source by interrupting automatically the electric power source circuit when a composite video signal is stopped like the completion of the television broadcasting. CONSTITUTION:When a synchronizing detecting circuit 11 receives a vertical synchronizing signal Vs, a transistor TR synchronizes with the synchronizing signal Vs and repeats ON and OFF. A capacitor C repeats the charging and the discharging in accordance with the ON and OFF of the transistor TR. By completing the broadcasting, the input of the synchronizing signal Vs is stopped, and then, the transistor TR is fixed to the off condition, as the result, a charging voltage Vc of the capacitor C rises to the threshold or above specified beforehand. When the voltage of the threshold or above is inputted, an inverter INV inverts the output and outputs it to a relay driving circuit 121. The relay driving circuit 121 operates a relay circuit 122 and changes over an electric power source circuit 13 to the off condition.
|
