| 摘要 |
PURPOSE:To prevent the generation of noise by forming a closed loop comprising a delay circuit and an amplifier when no input of a television signal exists and constituting a closed loop and an oscillation circuit while the gain of the closed loop is set to >=1. CONSTITUTION:When a state without a signal is generated while a reproducing head 11 reaches the 1st track position from the home position, a DOC pulse is generated, a changeover switch 13 is thrown to the position of other contact 13b, a closed loop comprising a 1H delay circuit 15, a resonance circuit and an amplifier 16 is formed to constitute an oscillation circuit. In the closed loop, the oscillation is started at a frequency near the frequency modulation carrier of a television video signal recorded on a magnetic disc and the oscillation signal is fed to a reproducing/demodulation circuit 14. A reproduced video signal Sv from the reproducing/demodulation circuit 14 reaches a constant DC level during this time. Thus, the generation of noise when the signal absence state continues longer is prevented.
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