Two channel audio scrambling system
US4654705A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 30, 1983 |
| Grant date | Mar 31, 1987 |
| Priority date | — |
| Expiry date | Dec 30, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/167
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A two channel audio scrambling circuit for a television signal encoding system includes synchronized digital carrier switching means for deriving two suppressed carrier, switched audio signals that are 90 degrees apart, and combining them into a single output signal. A digital phase shifter, supplied with a carrier related to the horizontal line frequency develops properly phased outputs for controlling electronic switches to produce two phase displaced digital carrier switching signals. A plurality of scrambling modes are determined by logic means under control of a vertical interval signal, a video inversion signal and a tone signal input for controlling the digital phase shifter to change the carrier frequency. Complementary decoding circuitry for recovering the so-encoded audio signals is also described.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.