Abstract: The present invention is directed to an inversion scrambler and unscrambler having pseudo-randomly controlled polarity-reversing switches to invert and re-invert, respectively, an audio signal so as to restrict the intelligent dissemination of the audio signal. To improve security of the scrambled signal, the audio signal is concealed prior to scrambling. Concealment includes clamping the original audio signal to a predetermined value and optionally offsetting this clamped signal prior to scrambling. The concealed signal is scrambled by inverting contiguous portions of the signal at pseudo-random intervals, accomplished by a polarity-reversing switching network controlled by a pseudo-random code generator. Upon unscrambling, artifacts will appear at the inversion points of the unscrambling signal, due to bandwidth limitations inherent in any transmission path.

Abstract: Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency.