| 摘要 |
PURPOSE:To detect accurately the tracking state by applying an FM signal reproduced by a video head to a tuning amplifier and a demodulated video signal to an input terminal of a synchronous separating circuit so as to bias the tuning amplifier by the output of the circuit. CONSTITUTION:The input terminal of the tuning amplifier 13 is connected to a connecting point between a reproducing amplifier 2 and a limiter 3 and the output terminal is connected to an input terminal of a detector 7. The input terminal of the synchronous separating circuit 14 is connected to a connecting point between an FM demodulator 4 and an output terminal 5 and the output terminal is connected to a bias input terminal of the tuning amplifier 13. The FM signal reproduced by the video head is branched from the pre-stage of the limiter and applied to the input terminal of the tuning amplifier, and this output is applied to the input terminal of the detector. The video signal demodulated at the post-stage of the limiter is applied to the input terminal of the synchronous separating circuit, this output is used as a bias of the amplifier and the amplifying operation is performed only during the period of the synchronizing signal of the video signal. |
