| 摘要 |
PURPOSE:To completely prevent the theft of a recording by recording a recording signal mixed with a theft inhibition instruction signal occupying a narrow frequency band in the vicinity of a specified frequency to a composite video signal within a vertical scanning period onto a recording medium. CONSTITUTION:A switch SWS is turned off at a timewise position corresponding to each pulse in a composite synchronizing signal by a switching pulse generated by a switching pulse generating circuit SPG. Thus, when the switch SW is turned on only for one vertical scanning period at every sec, a signal generated by the signal source SG of the theft inhibition instruction signal is supplied to an adder ADD during a period other than the period when each pulse of the composite synchronizing signal exists in the one vertical scanning period while the switch is turned on. A composite video signal mixed with the signal generated from the signal source SG being the theft inhibition instruction signal is outputted from the adder ADD and supplied to a recording section RD.
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