| 摘要 |
PURPOSE:To make the switch for switching operation unnecessary and improve the reliability, by detecting the synchronizing signal in the video signal from a VTR connected in the external and switching the VTR to the reproducing signal monitor and the receiving operation of a TV broadcast in accordance with the presence and absence of the synchronizing signal. CONSTITUTION:The output of a video detecting and amplifying circuit 5 of a TV picture receiver is applied to one input of the first switching circuit 7, and the output of a sound detecting and amplifying circuit 6 is inputted to one input of the second switching circuit 8. A video input terminal 9a of a VTR9 connected in the external is connected to the other input of the circuit 7, and a sound input terminal 9b is connected to the other input of the circuit 8. The third switching circuit 10 is provided, and a voltage +B is supplied to each circuit of the TV picture receiver by this circuit 10, and a switching control signal is applied to circuit 7 and 8. The synchronizing signal from the VTR9 is detected by a synchronizing signal separating circuit 11 connected to the input terminal 9a and is compared with the fly-back pulse in a comparing circuit 12; an if they coincide with each other, the circuit 10 is controlled to switch the VTR9 to the receiving state automatically. |
