| 摘要 |
PURPOSE:To prolong the lifetime of a unit by eliminating fruitless power supply by cutting off power supply to a post-amplification part by a switching circuit provided between a power circuit and the post-amplification part when detecting a TV signal by a detection part. CONSTITUTION:Between input terminal 5 and output terminal 15 of a community receiver, pre-amplification part 7, detection part 11 and post-amplification part 12 are connected in series, and power circuit 16 is provided which supplies power to pre-amplification part 7 and post-amplification part 12 to supply the output of circuit 16 direct to pre-amplification part 7. Further, power is supplied to post-amplification part 12 by way of switching circuit 20 and detection circuit 21 which detect the output of detection part 11 is provided to switching circuit 20; and switch element 23 is controlled by the output signal of this circuit 21, and power is supplied to post-amplification part 12 when detection part 11 generates an output or cut off when not, thereby inhibiting fruitless power supply to post-amplification part. |
