| 摘要 |
PURPOSE:To obtain an analog optical picture transmitter not giving adverse effect on a voice signal sent simultaneously even when an excess signal other than a picture signal is received. CONSTITUTION:A coupling section 3 applies frequency division multiplex to a picture signal S1 received from a picture signal input terminal 1, whose amplitude is limited by a diode limiter 8 and a frequency modulation signal S3 generated in response to the voice signal S2 from an audio signal input terminal 2. When a synchronizing signal detection section 9 cannot detect a synchronizing signal from the picture signal S1, an undetection signal S5 is produced. A pulse frequency modulator 4 produces a pulse frequency modulation signal S6 in response to the frequency division multiplex signal S4 and changes a center frequency of the pulse frequency modulation signal S6 upon the receipt of the undetection signal S5. A laser drive circuit 5 produces the laser drive output S7 in response to the pulse frequency modulation signal S6 and the laser diode 6 produces an optical signal in response to the laser drive output S7. |
