H - Electricity – 04 – N
Patent
H - Electricity
04
N
350/30
H04N 7/16 (2006.01) H04N 7/167 (2006.01)
Patent
CA 1228153
21 ABSTRACT: In a television receiver for a transmission system in which the vision signal and the audio/data signals are scrambled to allow only for their authorized reception, a low rate encrypted signal present at an output (11) of a sound/data signal processor (10) is decrypted and employed to periodically set (say once every one or two seconds) a master pseudo random pulse generator (12B) producing an output of pseudo random configuration at frame rate. It is used on the one hand to periodically set a vision slave pseudo random pulse generator (15) to produce an output of pseudo random configuration at line frequency. This is applied to an input S of the vision processor (8) for the line-by-line de-scrambling of the vision signal. The output of the master pseudo random generator (12B) is also used to periodically set a number of further slave pseudo random pulse generators (17, 18, 19) which produce outputs of pseudo random configuration at an intermediate frequency applied to inputs S1, S2, S3 of the processor (10) and which form the respective keys for the de-scrambling of the scrambled sound/data compo- nents. The advantage obtained is that a low rate encryption key need only be transmitted to produce the required scrambling keys for both vision and sound/data.
456474
Crowther Gerald O.
Mason Arthur G.
Koninklijke Philips Electronics N.v.
Van Steinburg C.e.
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