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AssigneeNorth American Philips Corporation
InventorsJeffrey L. Cooper, Brian C. Johnson
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A method for scrambling and descrambling television programs in which the horizontal synchronizing information is suppressed at a CATV supplier's head-end and then regenerated at the subscriber's converter. The pulse frequency is multiplied by a factor N/M, in which N and M are integers thereby generating a synthesized pulse stream which is, in turn, encoded with data identifying the values for N and M. This encoded pulse stream is modulated onto the audio subcarrier wave in the TV video signal and transmitted to the converter. The converter then demodulates and recovers the encoded pulse stream, decodes the same to recover the identifying data, using this data to obtain the correct values for N and M which have been transmitted separately on a digital data channel. The converter then multiplies the synthesized pulse stream by M/N regenerating the horizontal synchronizing pulse stream and inserts the same into the TV video signal at the proper phase.
A method for scrambling and descrambling television programs, in which selected television programs, in the form of composite TV video signals having a stream of horizontal synchronizing pulses therein, are scrambled at the transmission end and then descrambled, when authorized, at the receiving end;
Apparatus for scrambling and descrambling television programs, in which selected television programs, in the form of composite TV video signals having a stream of horizontal synchronizing pulses therein, are scrambled at the transmission end and then descrambled, when authorized, at the receiving end;
Apparatus for scrambling television programs, in which selected television programs, in the form of composite TV video signals having a stream of horizontal synchronizing pulses therein, are scrambled at the transmission end and then descrambled, when authorized, at the receiving end;
Apparatus for descrambling television programs, which programs, in the form of composite TV video signals, have been scrambled by having the horizontal synchronizing pulse stream contained therein suppressed and by combining therewith an encoded synthesized pulse stream which is formed by multiplying the pulse frequency of the horizontal synchronizing pulse stream by a factor N/M, N and M being integers, and by encoding the synthesized pulse stream with in-channel data including data concerning the values for N and M as well as the phase of the horizontal and vertical synchronizing pulses;
Dependencies are inferred from the claim text.