A video scrambler/descrambler concept for the pal format

To obtain high security scrambling of PAL video signals, the so-called line rotation principle is adopted. A low cost solution is attained by making use of the modern l.s.i. components recently made available for manufacturers of digital television sets. A data link to the subscribers is established utilizing unused video lines. The availability of low-cost videotex l.s.i. circuitry has led to the choice of the videotex format for the data channel. A laboratory prototype has demonstrated the line rotation principle and tests have been carried out both in CATV networks and on terrestrial links with very satisfactory results. However, the video signal is distorted in transmission links with line tilt. Methods for reducing the effect of line tilt are presented.