| 摘要 |
PURPOSE:To prevent the band of a radio frequency signal from exceeding a permitted limit by controlling the device that a radio frequency is transmitted only when the output of an AND between the detected outputs of a vertical synchronizing signal or a horizontal synchronizing signal is generated. CONSTITUTION:A diveo signal input is branched from input of an LPF1, detected at an amplitude detecting circuit 5 and a DC output in response to the amplitude is generated. Further, the signal is applied to a synchronizing signal detecting circuit 6 and a vertical synchronizing signal or a horizontal synchronizing signal in the video signal is detected. The circuit 6 generates a DC output corresponding to the presence when the synchronzing signal is detected. Both outputs are applied to an AND circuit 7, the AND circuit 7 ANDs both outputs and only when both outputs exist, the circuit 7 generates the output. A switch circuit 2 is controlled by the output of the circuit 7, is turned on only when the circuit 7 generates an output and the output of the LPF1 is given to an FM modulator 3 as an input. Further, a radio frequency signal is generated and transmitted via an antenna 4. |
