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Abstract

A video signal synthesizer operable to provide a multiplex video signal for producing a picture-in-picture effect on a display screen of a display device, for example, a cathode ray tube. The video signal synthesizer utilizes a PLL (phase-locked loop) circuit to generate a carrier signal synchronized with a color burst signal contained in the composite video signal for the reproduction of the main picture. The carrier signal is first delayed by a delay circuit and then utilized to remodulate the sub-picture signal which has been compressed with respect to time. This remodulated sub-picture signal is then subjected to time-division multiplexing through analog switch assembly. The delay time of the delay circuit is set so that both color subcarrier signals of the main picture and sub-picture signals may be matched in phase. Hence, the time-division multiplexing of the main picture signal and the sub-picture signal is possible without altering the characteristics of the color composite video signal. Thus, the necessity of the main picture signal being demodulated and modulated can be obviated.

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First Claim