| 摘要 |
PURPOSE:To reduce flickering of the screen and degradation of the picture quality generated conventionally by ciphering, by switching the mode only when average gradation of the video signal changes while holding the random property. CONSTITUTION:By supplying the 6-line counter output through an inverter to one input of AND gate 35 connected to the load input of register 13, random numbers are given from code generating part 1 for the first-the fifth lines and are given from code generating part 2 for the sixth line. The inhibition pulse from gate 31 is generated when it is necessary that the program discrimination signal is inserted to the television signal. When gate 31 is driven, contents of parallel-series register 36 are read out in series and are given to OR gate 32. The output of OR gate 32 is supplied to program designation logical operation circuit 33, and the output of this circuit gives signals A-D to determine the polarity mode of the encoder. |
