Addressable subscription television system having multiple scrambling modes
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United States of America Patent
Stats
-
Dec 29, 1987
Grant Date -
N/A
app pub date -
Oct 29, 1985
filing date -
Oct 29, 1985
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A multimode scrambling system for video signal transmission systems is described. The system provides for baseband video scrambling controlled by a central originating computer facility. The scrambling of each field of a video changes on a per field basis. The video signal is scrambled in several modes including vertical interval scrambling, alternate line inversion, bogus sync pulse generation, video compression and video offset techniques. A scrambling sequence is sent by a unique algorithm, sent during the vertical interval to each system decoder. The algorithm is reordered for each of a plurality of fields of the video signal and the reordering position is identified by a unique synchronization pulse transmitted during the vertical interval of the video signal. Additional security measures are provided to inhibit a subscriber from avoiding a transmitted disable command, or an attempt to invade the subscriber decoder mechanical packaging security.
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Family
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Cited Art Landscape
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