VIDEO SCRAMBLE DESCRAMBLE DEVICE

摘要

PURPOSE:To improve the security against illegal descrambling and to reduce the effect on a voice signal by applying AM modulation to a transmission voice signal independently of the period subject to scrambling and no scrambling. CONSTITUTION:A control circuit 20 generates a prescribed timing pulse during the period of a horizontal synchronizing signal to be scrambled and the horizontal synchronizing signal not to be scrambled. A voice IFAM modulation circuit 18 applies AM modulation to a transmission voice signal by using a pulse from the control circuit 20. The output is given to an RF modulator 16 and mixed with a video signal subject to scrambling processing and converted into an RF frequency.