Method and system for scrambling information signals
US5091935A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 10, 1986 |
| Grant date | Feb 25, 1992 |
| Priority date | — |
| Expiry date | Apr 10, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/171
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and system for scrambled transmission of an information signal having a regular, repeating information rate from which a receiver of the information signal derives synchronizing information as in a television video signal. The information signal is summed with a scrambling signal having a frequency which is a function of the information rate plus an error quantity within a predetermined bandwidth, namely that of the synchronizing circuitry in the normal information receiver. The sum of the information signal and the scrambling signal is transmitted as the scrambled information signal. In a television scrambling system, the information signal is a television video signal and the information rate is a video synchronizing rate, preferably the horizontal line rate. The television information signal also includes an audio signal which is scrambled by mixing the audio signal with a carrier signal realted to the video synchronizing rate, to produce a lower sideband which is transmitted as the television audio signal. The frequency of the scrambling signal F.sub.j is defined by the equation F.sub.j =A.multidot.F.sub.h +B, where A is an integer, B is the value error quantity, and F…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.