Importance

Loading Importance Indicators...

Abstract

A method and apparatus for encoding and decoding of standard television signals are provided for enabling reception thereof in an intelligible manner only by authorized subscribers. The scrambling of the video signals is effected by inversion of the video signals of some horizontal scan lines on a pseudo-random basis to produce a picture having some video signals inverted and others not inverted which is unpleasant to view and virtually unintelligible. The scrambling of the audio signals is effected by conversion of analog audio signals to coded digital audio signals. A plurality of unique pulse coded control signals consisting of 32-bit binary pulse trains are transmitted separately to identify individual authorized subscribers and to provide information needed to unscramble the scrambled video and audio signals. When there is a comparison between one of the pulse-coded control signals and a unique address code stored at a particular subscriber's receiver, unscrambling of the video and audio signals occurs in the same sequence as used for scrambling so as to provide restored video and audio signals without degradation in picture and sound qualities.

Loading the Abstract Image...

First Claim