| 摘要 |
PURPOSE:To cause unauthorized copying preventing operations to be carried out smoothly even if the circuit constant of a VTR constituting part fluctuates, by providing the constitution of a composite video signal recorder itself having an unauthorized copying preventing means. CONSTITUTION:Presence of additional signals for preventing unauthorized copy ing which are constituted of the combination of artificial horizontal synchroniz ing pulses and pulses having forms as if they are projected in the white level direction at the time position succeeding the horizontal synchronizing pulses in the vertical blanking period of composite video signals, is detected by means of a band-pass filter BPF, detecting circuit DET, comparator COMP, U-type flip flop DFF, shift register SR, and NAND circuit NAND. Then, only when the additional signals for preventing unauthorized copying exist in all of plural continuous vertical scanning periods, a switch SW is set to its turned-off state by the low-level output of the NAND circuit and supply of the composite video signals supplied to an input terminal 4 to a video signal recording system SDS is prevented.
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