Television security system
US4074311A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 1976 |
| Grant date | Feb 14, 1978 |
| Priority date | — |
| Expiry date | Jun 18, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K2203/14
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for subscription TV security which is comprised of a scramble signal generator which adds a modulated RF carrier signal to the TV channel transmission. Preferably the frequency of the scramble signal generator is selected to fall within the band of frequencies of the TV channel between the video carrier and the audio carrier. The TV channel is transmitted to receivers encoded with the scramble signal carrier providing false and misleading information, preventing the receiver from reconstituting a coherent picture or sound while this scramble signal is present. The transmitted signal is decoded, (i.e. scramble signal removed), restoring regular reception by filtering with a sharply tuned high-Q notch filter attached to the drop line going to a TV receiver. By careful selection of the band width and attenuation of the filter and pre-emphasis of the channel band, degradation of the video information is prevented.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.