| 摘要 |
PURPOSE:To obtain a device hard to listen and watch secretly, high in reproduced sound and picture and having a decoding section suitable for large scale integration by sampling digital sound signals and enciphered information and deciphering enciphered video signals and sound signals in a device that encipheres and transmits video or voice by CATV, charged television etc. CONSTITUTION:The content of a buffer memory 20 is read out at frequency 2fH twice that of horizontal scanning, and converted to analog sound signals by a D-A convertor 21. On the other hand, if speed of transmission of data transmitted in the vertical flyback time is equal to that of sound data, data of 440 bits can be superposed in 1H period. Data of 5H-7H, 268H-270H are stored in a buffer memory 14, information data are deciphered in a deciphering circuit 15, and a deciphered signals as to whether the video signals are polarity inverted or not and deciphering code when the sound data are enciphered are outputted. The decision signal as to polarity inversion or not is supplied to an inversion switching circuit 16, and polarity inverted video signals are restored to video signals of fixed polarity. |
