| 摘要 |
PURPOSE:To display an interrupted camera output, by detecting a reception channel in operation, generating a high frequency signal equal to a channel carrier frequency, amplitude-modulating with a video signal of a TV camera and inputing the signal to an antenna terminal by switching. CONSTITUTION:A local oscillation signal leaked to an antenna terminal 1 of a TV in operation is received at a reception channel detecting circuit 2, and a high frequency signal in a frequency equal to a carrier frequency of the detected reception channel is generated at a carrier wave generating circuit 3. The signal from the circuit 3 is amplitude-modulated 4 with an interrupting video signal outputted from a TV camera provided a front gate. When a push button switch SW is depressed, a switching contact (r) of a switching circuit 6 for a prescribed time set with a timer T is changed over to the (b), an interrupting TV signal from the circuit 4 is inputted to a terminal 1 and the picture of the camera 5 is displayed. After a prescribed time is over, the contact (r) is changed over to the (a) and the TV broadcast received on an antenna 7 is again displayed. |
