| 摘要 |
PURPOSE:To simplify the circuit scale by repeating alternately a period when a pseudo synchronizing signal is superimposed and a period not superimposed, inverting a phase of a video signal for the period when the pseudo synchronizing signal is superimposed and using the result as a scramble signal. CONSTITUTION:A pseudo signal addition section 2 generates a pseudo synchronizing signal with a predetermined pulse width and amplitude and provides the signal to a phase inversion section 3 under the control of a scramble timing control section 7. The inversion section 3 inverts the phase of only a video signal for a time Ts being a time when the pseudo synchronizing signal is superimposed to obtain a video signal in the scramble state. A signal from a voice signal generating section 4 is subject to FM processing at an FM modulation section and a timing signal addition section 6 uses an amplitude modulation means to superimpose the timing signal for the time Ts only. The start point for a horizontal blanking period when the pseudo synchronizing signal is superimposed is made coincident and the period is set equal to that of the pseudo synchronizing signal. Thus, a voice signal superimposed on the timing signal is mixed with the signal from a video signal AM modulation section 8 at a mixer 9 and the result is outputted. |
