| 摘要 |
PURPOSE:To avoid a sense of displeasure in a video and an audio signal caused at interblock of the signal by cutting off an audio output in the absence of a broadcast signal or a base band signal, cutting off noise as to the video signal also and outputting a monochroic signal on a display device. CONSTITUTION:Since no synchronizing signal is extracted at a collector of a transistor(TR) Q1 of a synchronizing signal separator circuit in the absence of a broadcast signal, no potential is applied to a base of a TR Q2, which is turned off and the collector reaches a high level via a pullup resistor R6. In this case, a switch 51 is closed to apply muting to an audio signal. Moreover, a switch 52 is closed to avoid the invasion of a noise signal to a video signal processing circuit 2 thereby avoiding a white noise from being displayed on a CRT 5. Thus, a sense of displeasure due to unpleasant video image or audio noise is eliminated. |
