| 摘要 |
PURPOSE:To suppress a signal in the video signal period other than the synchronizing pulse period basing on the reference level signal to attain descrambling by transmitting the reference level signal together with a timing pulse from the transmitting side. CONSTITUTION:Video signals of a terminal 21 are modulated by an AM modulator 22 and supplied to a period signal suppressing device 23, and suppressed only in synchronizing period by the pulse signal from a terminal 30, and the suppression ratio is controlled by DC voltage from a terminal 31. Sound signals of a terminal 25 are frequency modulated by an FM modulator 26, and AM modulated by the timing pulse signal in an AM modulator 27, and the degree of modulation is controlled by the DC voltage applied to the terminal 31. In such a case, the output level can be made equal by matching of the degree of suppression in the suppressing device 23 and the degree of suppression in the modulator 27. Accordingly, a reference signal including information of the suppression ratio can be loaded on transmitted scramble television signals together with the timing pulse signal for descrambling. |
