Multichannel subscription television system
US4330794A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 25, 1980 |
| Grant date | May 18, 1982 |
| Priority date | — |
| Expiry date | Feb 25, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/1713
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Sinusoidal timing reference signals, each of which is associated with a different suppresed-sync scrambled-priority television channel signal, frequency modulate associated carrier frequency signals for producing modulated carrier signals that are combined with a continuous wave (CW) sinusoidal carrier frequency signal. After low-pass filtering to block harmonic frequencies that may interfere with the video carriers of composite television signals, only the fundamentals of the CW and modulated carrier signals are combined with non-scrambled and/or scrambled composite television signals for transmission to subscriber's equipment. In a descrambler at a subscriber location, the CW carrier signal is mixed with the modulated carrier signals to produce frequency modulated IF signals containing timing information for associated priority television channel signals. Upon request of a subscriber, a particular IF signal is demodulated to reproduce a timing reference signal here that is operated on to produce timing pulses that are slightly wider than the pulse width of, and delayed in time with respect to, suppressed horizontal blanking pulses carrying synchronization pulses in the associated…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.