| 摘要 |
PURPOSE:To simplify a circuit constitution, and to improve a furtive glance- proofing property by performing the level compression of a horizontal synchronizing signal included in a composite video signal to plural different kinds of levels irregularly, and overlapping a restoration pulse having the compression information on a sound carrier wave making synchronize with the horizontal synchronizing signal. CONSTITUTION:A level signal generated at a compression level signal generator 10 is inputted to a variable attenuator 2, and also, it is inputted to a restoration pulse generator 9. At the restoration pulse generator 9, the horizontal synchronizing signal is inputted from a terminal 19 to monostable multivibrators 20 and 21, and two kinds of pulses having different time widths are outputted. The restoration pulse is inputted to a timing pulse modulator 6, thereby, a sound IF signal is modulated, then being inputted to a mixer 3. On the mixer 3, a video IF signal scrambled at the variable attenuator 2 by a timing pulse from the restoration pulse generator 9, and the level signal from the compression level signal generator 10, is added. At the mixer 3, the video IF signal and the sound IF signal are mixed, and a scrambled IFTV signal is outputted from a terminal 4. |
