| 摘要 |
PURPOSE:To prevent a picture from duplicated recording by giving an inconvenience to a reproduced color picture, by recording the pulse signal of a prescribed frequency as a multiple signal in the range of the video signal that is not substantially reproduced within the screen of a color TV picture receiver. CONSTITUTION:The standard color video signal (a) of the NTSC system is supplied to the input terminal 21, and the luminance signal contained in the signal (a) is extracted out of the low pass filter 22 with a band limitation with which the upper limit frequency is set at about 3MHz. Then the horizontal synchronous signal (b) is separated and delivered by the synchronous separating circuit 24 to be supplied to the delay multi 25 and the chrominance subcarrier generator 26 each. On the other hand, the band pass filter 23 extracts the carrier chrominance signal to supply it to the generator 26 and the chrominance signal converting circuit 27. These signals are supplied to the signal process circuit 29 via the mixer 28. Then the AND circuit 31 carries out a chopper between the composite color video signal and the DC level through the circuit 29. Thus the oscillation pulse that prevents a duplication is inserted into the position within a screen where no reproduction is carried out. In such a way, a duplicated picture recording can be prevented. |
