| 摘要 |
PURPOSE:To prevent the over modulation-driving of a light emitting element and the distortion of a voice carrier due to an excess output signal of white character signal, etc., and a limiter from occurring by superposing a video signal, after limiting its amplitude level, with the sound carrier wave to drive the light emitting element. CONSTITUTION:A VHF signal received by a VHF signal receiving antenna 1 is converted to an IF signal by a tuner 2, then detected by a video detector 8 and a voice detector 9. And the excess output signal components of such as white character signal is limited within a specified level by a limiter 4 (signal-amplitude limiting circuit). Thereafter the signal is superposed with the voice carrier wave signal by a video-voice synthesizing circuit 10. A resulting signal is made light signal 7 by driving the light emitting element 6 by a light emitting element driving circuit 6, and is outputted. In such a way, at the time of optically transmitting the picture of a demodulated TV signal in which the video is selected, the over modulation of the light emitting element and the distortion of the voice carrier can be prevented. |
