| 摘要 |
PURPOSE:To prevent the band of an output radio frequency signal from being spread to a limit or over by branching and detecting the LPF input of a video signal and a sound signal and controlling a television signal output to a prescribed level by the synthesized output of both detected outputs. CONSTITUTION:A video signal input and a sound signal input are branched from the input of the LPF1, 2 respectively, detected (8,9) and a DC output in response to the amplitude is generated and after this output is subject to a prescribed amplification via amplifiers 10, 11, the output is applied to a control signal synthesis circuit 12. The circuit 12 consists, e.g., of an OR circuit and generates an output when both inputs are synthesized and any of them exceeds a prescribed level. A control circuit 5 consists, e.g., of a switch circuit, is turned off while being added with the output of the circuit 12 as a control signal so as to cut off the input to a modulator 6 from the input synthesis circuit 3, and then the excess input to the modulator 6 is prevented and the frequency band of an output radio frequency signal is not spread in excess of the limit. |
