Secure video distribution system
US4841569A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 30, 1987 |
| Grant date | Jun 20, 1989 |
| Priority date | — |
| Expiry date | Dec 30, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K2203/14
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A video distribution system (e.g., CATV or MATV) employs at least one channel having a reception-defeating jamming signal which changes frequency periodically or, preferably, randomly. The signal originating head end distributes information characterizing the operative frequency of the jamming wave. At controller apparatus for authorized viewers, the jamming frequency specifying data is employed on a frequency agile basis of heterodyne the protected channel into a proper (fixed) frequency relationship with a notch band suppression filter to remove the jamming signal. The secure channel with the jamming wave removed is then again shifted to its original or other intended frequency to permit normal reception either directly by a standard television receiver, or via a frequency converter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.