Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1974-12-26
1976-12-21
Wilbur, Maynard R.
Facsimile and static presentation processing
Facsimile
Recording apparatus
325 60, 325 65, H04N 144
Patent
active
039990052
ABSTRACT:
A method and system for scrambling amplitude-modulated or frequency-modulated signals at a transmitter and descrambling the scrambled signals at a receiver. The scrambling is effected at the transmitter by shifting the phase of only the carrier component of the modulated signal by from 80 to 100 carrier degrees, preferably exactly 90 carrier degrees, the phase shift either advancing or retarding the carrier component out of its proper phase relationship with the side band components of the modulated signal in the transmitted version of the modulated signal. The descrambling of the transmitted version of the modulated signal is effected in a receiver, prior to demodulation therein, by restoring the carrier component back into its proper phase relationship with te side band components of the modulated signal. Without such restoration, a scrambled AM signal transmission substantially appears to be an FM signal at an AM demodulator of a receiver and an FM signal transmission substantially appears to be an AM signal at an FM demodulator of a receiver. The method and system thus have particular utility in connection with pay television, since they involve a technique whereby a signal scrambling may be readily carried out at a pay television transmitter on the video AM portion of a television signal or on the audio FM portion thereof or on both portions thereof and a descrambling of the scrambled signal may be readily carried out at a subscriber's television receiver.
REFERENCES:
patent: 3081376 (1963-03-01), Loughlin et al.
patent: 3084329 (1963-04-01), Clay
patent: 3353099 (1967-11-01), Hayasi et al.
patent: 3852519 (1974-12-01), Court et al.
patent: 3896262 (1975-07-01), Hudspeth et al.
Buczinski S. C.
E-Com Corporation
Wilbur Maynard R.
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