Patent US4254435A successfully refreshed from Google Patents.
US4254435A
Expired / Lapsed
US
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Noise eliminator for television synchronizing signal separating circuits
Assignee: Grass Valley Group Inc
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Filing: 1979-04-30
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Granted: 1981-03-03
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Expires: 1999-04-30
Abstract
Abstract A circuit for reducing the effects of negative-going impulse noise in composite television video signals has on sync separators is disclosed. A variable output current source is used to supply rundown current to a dc restorer in a sync separator. A retriggerable monostable multivibrator is triggered by negative-going impulse spikes in the composite video signal. The output of this multivibrator is coupled to the current source to increase its output and therefore decrease the time required for the dc restorer to recover from the negative spike.
Inventors
- 👤 Birney D. Dayton
- 👤 William L. Rorden
- 👤 Leon J. Stanger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:53
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/21; H04N5/213
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
135 words
A television synchronizing signal separating circuit comprising: a dc restoration circuit for receiving a composite video signal and adding a dc voltage level thereto, the recovery time of said restoration circuit depending upon the amount of current applied thereto; a variable current source for supplying current to said dc restoration circuit, the output level of said variable current source varying according to the level of an input pulse applied thereto; an amplitude separator coupled to receive a dc-restored video signal from said dc restoration circuit for producing a separated sync signal therefrom; and a retriggerable monostable multivibrator having a trigger input terminal for receiving said separated sync signal and an output terminal said output terminal being connected to said variable output current source for applying said input pulse thereto and thereby increasing its output current.
Claim 2
Dependent Claim
135 words
A television synchronizing signal separating circuit comprising: a dc restoration circuit for receiving a composite video signal and adding a dc voltage level thereto, the recovery time of said restoration circuit depending upon the amount of current applied thereto; a variable current source for supplying current to said dc restoration circuit, the output level of said variable current source varying according to the level of an input pulse applied thereto; an amplitude separator coupled to receive a dc-restored video signal from said dc restoration circuit for producing a separated sync signal therefrom; and a retriggerable monostable multivibrator having a trigger input terminal for receiving said separated sync signal and an output terminal said output terminal being connected to said variable output current source for applying said input pulse thereto and thereby increasing its output current.
Claim 3
Dependent Claim
25 words
The sync separator circuit according to claim 1 wherein said dc restoration circuit comprises a clamping diode and means for storing a dc restoration voltage.
Claim 4
Dependent Claim
19 words
The sync separator circuit according to claim 1 wherein said variable output current source comprises a current mirror circuit.
Claim 5
Dependent Claim
24 words
The sync separator circuit according to claim 1 wherein said amplitude separator comprises a pair of differentially coupled transistors of the same conductivity type.
Claim 6
Dependent Claim
40 words
The sync separator circuit according to claim 4 wherein said differential pair compares the voltage level of said dc restored video signal to a reference voltage approximately equal to fifty percent of the average voltage level of the sync signal.
Claim 7
Dependent Claim
23 words
The sync separator circuit according to claim 1 further comprising a buffer amplifier disposed between said dc restoration circuit and said amplitude separator.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-02 | 1984-09-01 | 1985-03-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-02 | 1988-09-01 | 1989-03-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-02 | 1992-09-01 | 1993-03-03 | $7700.00 | Window Closed / Lapsed |