US 4,434,436 AGranted

Addressable premium channel obfuscation device for cable television systems

AssigneeBruce Merrill

InventorsGayheart C. Kleykamp, Sam Goldwater, Charles L. Salsbery

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Abstract

An obfuscation device for use in cable television systems includes a memory for storing a plurality of channel status bits. The state of each channel status bit corresponds to the authorization or non-authorization of a particular channel. The obfuscation device includes a circuit for selecting a number representing a frequency and a circuit for generating an obfuscation signal that randomly varies about the selected frequency. The obfuscation device uses the selected number to address a location of the memory to fetch the channel status bits corresponding to the respective residences for the channel in which the selected obfuscation frequency lies. The fetched status bits are applied at random time in a predetermined gating period to gating circuits that enable the generated obfuscation signal to be superimposed randomly, with respect to timing, on the program signal of the channel in which the obfuscation frequency lies to obfuscate the television picture received by viewers of television sets in the residences not authorized to receive the channel in which the obfuscation frequency lies.

Claims23

Dependent claims

A method of preventing piracy of television programs supplied by a cable television system including a communication center applying to a main cable a plurality of program signals each having a frequency range within a respective one of a plurality of respective channels, various residences being authorized to receive various ones of the programs represented by said program signals, said cable television system also including a plurality of drop cables coupled to said main cable for delivering said program signals to said residences, said method comprising the steps of:

(a) loading an addressable memory with a plurality of channel status bits, each of said channel status bits having a state that represents the authorization or non-authorization of a particular one of said residences to view a program on a particular one of said channels;
(b) selecting an obfuscation signal frequency that is within a selected one of said channels, said obfuscation signal frequency being one of a plurality of obfuscation frequencies that are within respective ones of said channel frequency ranges, said memory having a plurality of addressable locations each corresponding to a respective one of said obfuscation signal frequencies, each of said addressable locations containing a plurality of said channel status bits respectively representing the authorization or non-authorization of respective ones of said residences to view the programs on respective ones of said channels;
(c) generating an obfuscation signal having a carrier frequency equal to the obfuscation signal frequency selected in accordance with step (b);
(d) addressing the location of said memory corresponding to said obfuscation signal frequency selected in accordance with step (b) to obtain the channel status bits therefrom;
(e) superimposing said obfuscation signal of step (c) onto the program signals conducted by the ones of said drop cables coupled to television sets in the ones of said residences indicated by the channel status bits obtained in step (d) to be not authorized to view the program represented by the program signals of the channel in which the obfuscation signal frequency selected in accordance with step (b) lies;
and
(f) repeating steps (b) through (e) for another of said channels.

4 more elements

In a cable television system including a main cable for conducting a plurality of program signals each having a frequency range within various ones of a plurality of channel frequency ranges, a plurality of drop cables coupled to said main cable for delivery of said plurality of program signals to respective ones of a plurality of residences, wherein various ones of said residences are authorized to receive only certain ones of the television programs represented by said plurality of programs signals, a theft prevention device for preventing unobfuscated reception of television programs for said residences, said program theft prevention system comprising in combination:

(a) first means for storing a plurality of channel status bits, the state of each of said channel status bits corresponding to the authorization or non-authorization of a particular one of said residences to view a program on a particular one of said channels, said first means being addressable to effect fetching of a one of said channel status bits corresponding to a particular one of said channels;
(b) second means for sequentially generating a plurality of obfuscation signals, said plurality of obfuscation signals having frequencies that lie within respective ones of said channel frequency ranges;
(c) third means for selecting the carrier frequency of a present obfuscation signal, said present obfuscation signal being the one of said obfuscation signals next to be generated by said second means, said second means being responsive to said third means to generate said present obfuscation signal at said selected carrier frequency;
(d) fourth means responsive to said third means for addressing a location of said first means represented by said selectively determined frequency to fetch the channel status bits corresponding to one of said channels;
and
(e) fifth means responsive to said second means and said fourth means for superimposing said present obfuscation signal onto the program signal being conducted by drop cables connected to ones of said residences not authorized to receive the television program represented by the program signal conducted by those drop cables.

3 more elements

Dependencies are inferred from the claim text.