Transmission system
US4636854A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Jun 20, 1984 |
| Grant date | Jan 13, 1987 |
| Priority date | — |
| Expiry date | Jun 20, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/1675
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In a television receiver for a transmission system in which the video signal is scrambled to allow only for its authorized reception, a video signal processor (8) is provided in which the scrambled video signal is de-scrambled. 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 ramdom pulse generator (12B) producing an output of pseudo random configuration at the frame rate which is used to periodically set a video 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 processor (8) and forms the scrambling key for the line-by-line de-scrambling of the video signal. The sound/data components, which are packet multiplexed, are also scrambled at packet rate to allow only for their authorized reception, the sound/data signal processor (10) additionally performing the descrambling of the sound/data components. The output of the master pseudo random generator (12B) is also used to periodically set a number of slave pseudo random pulse generators (17, 18, 19)…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.