VIDEO TAPE COPY PREVENTING SIGNAL INSERTION RELEASING DEVICE

摘要

PROBLEM TO BE SOLVED: To obtain a video tape copy prevention signal insertion release device by which a user can simply insert/release a copy guard. SOLUTION: A video signal enters a synchronizing separator circuit and a video switch circuit after passing through a buffer. The synchronizing separator circuit generates a vertical synchronizing signal and a horizontal synchronizing signal for the video signal. A control signal for the video switch is produced by counting and processing the obtained two kinds of the synchronizing signals. Furthermore, oscillators 1, 2 generate a guard signal to be inserted to the video signal. The video switch selects the video signal directly received and the guard signal on the basis of the control signal of the video switch and provides an output of the selected signal. The outputted signal is amplified by an amplifier circuit and outputted as the video signal to which the guard signal is inserted. In the case of releasing the insertion of the guard signal, the guard signal from the oscillators 1, 2 is replaced with a usual signal such as a composite signal or a DC.