Method and apparatus for improving video scrambling and employing split snyc pulses
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United States of America Patent
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May 8, 1990
Grant Date -
N/A
app pub date -
Apr 29, 1988
filing date -
Apr 29, 1988
priority date (Note) -
Expired
status (Latency Note)
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Abstract
This invention discloses a new and improved method of scrambling video signals by inversion of the video information by splitting the sync pulse into plural portions and transmitting each portion of the sync pulse at a predetermined level. This improves the quality of the recovered video compared with other video inversion systems by rendering the video less sensitive to variations in the modulation depth of the modulator carrying the inverted signal, the demodulation sensitivity of the demodulator and the stability of the recovery circuits. The invention further provides additional security against pirating by allowing the scrambling circuit to operate in diverse modes, each of which will cause a TV to react differently should a conventional pirating device be employed. The invention also renders the signal capable of being transmitted with unmodified modulators of the type normally employed in the CATV industry.
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