Reference time detecting circuit
US4618891A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 20, 1983 |
| Grant date | Oct 21, 1986 |
| Priority date | — |
| Expiry date | Jun 20, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/08
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A reference time detecting circuit has a video signal supplied to first and second clamping circuits (40) and (70) of different time constants and a synchronizing signal is separated from the output signal from the first clamping circuit (40) of a longer time constant, while a reference time is detected from the output signal from the second clamping circuit (70) of a shorter time constant. Consequently, since the two clamping circuits (40) and (70) of different time constants are provided, the clamping circuit (40) of longer time constant generates a signal having a sync-tip portion of a predetermined voltage to perform the accurate vertical synchronizing separation from which an accurate masking pulse is formed, while the clamping circuit (70) of shorter time constant generates a signal having a pedestal portion with a noise suppressed to thereby positively detect the rising edge of the synchronizing signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.