CATV scrambling system with compressed digital audio in synchronizing signal intervals
US4688246A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 1985 |
| Grant date | Aug 18, 1987 |
| Priority date | — |
| Expiry date | Dec 20, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/085
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A CATV television system has the sync and color subcarrier reference information replaced in the horizontal blanking intervals with compressed digital audio data. The digital audio data is in the form of a modified duobinary signal having data sampling points selected to coincide with the zero crossings of a color reference subcarrier. A phase locked loop provides the master clock for the signal generator and the data sampler. A horizontal interval detector circuit recovers a 1.8 MHz CW signal of greater than one half line duration, followed by a white horizontal identification pulse of 4.7 microseconds width, that are supplied in place of the pre-equalizing, vertical sync and post equalizing pulses in the vertical interval. CODE 1TV60CATV
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.