| 摘要 |
PURPOSE:To easily overlap and output a video signal and a character and mark signal, by providing a means which generates a superimposing synchronizins signal phase- locked to the synchronizing signal of the video signal at the input time of the video signal. and outputs a phase locking oscillator output signal as a similar synchronizing signal at no input time of the video signal. CONSTITUTION:An inputtted video signal 101 is phase-compared with the outgoing output signal 102 of an oscillator 2 at a phase comparison circuit l, and a phase error signal 103 is inputted to the oscillator 2, and a reference signal 104 phase-locked to the synchorizing signal of the video signal 101 is outputted. The signal 104 is inputted to a synchronizing signal generation circuit 4 with the video signal 101, and a synchronizing signal 105 is generated, and the character and mark signal is added on the video signal 101 at a character/mark insertion circuit 5, then being outputted. When no video signal 101 is inputted, the reference signal 104 is impossible to take a phase lock, therefore, it is inputted to the synchronizing signal generation circuit 4 as the reference signal having a frequency adjacent to the frequency of the synchronizing signal of the video signal 101, and a similar synchronizing signal 106 is generated, then being inputted to the character/mark signal insertion circuit 5, and the character and marh signal driven by the similar synchronizing signal 106 is generated and outputted.
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