Patent US4688097A successfully refreshed from Google Patents.
US4688097A
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US
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D.C.-coupled video clamping circuit
Assignee: Arris Technology Inc
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Filing: 1986-10-30
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Granted: 1987-08-18
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Expires: 2006-10-30
Abstract
Abstract A d.c.-coupled video clamping circuit is disclosed for operation with normal video signals and sync suppressed scrambled video signals. For receiving normal video signals, a feedback path detects variations in sync tip level from a reference level and applies a corresponding control voltage to a d.c. signal amplifier, thereby to clamp and maintain the sync tip at a fixed (black) level. For receiving sync suppressed scrambled video signals, the feedback path is disabled and a fixed reference voltage is applied to the d.c. signal amplifier.
Inventors
- 👤 Wen T. Lin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:47
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/16; H04N5/18; H04N7/00; H04N7/16; H04N7/167; H04N7/171; H04N7/1713
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
148 words
A d.c.-coupled video clamping circuit comprising an input terminal , a d.c. signal amplifier having a first input for receiving normal or scrambled video signals coupled to said input terminal; feedback means connected to the output of said signal amplifier, said feedback means including means for detecting the sync tip level of a normal video signal and an error amplifier coupled to the output of said detecting means for producing an error signal representative of variations in the sync tip level from a desired reference level; and control means effective when in a first condition, when it is desired to receive a normal video signal, to apply said error signal to a second input of said signal amplifier, and effective when in a second condition, when it is desired to receive a scrambled video signal, to connect a reference voltage to said second input of said signal amplifier.
Claim 2
Dependent Claim
148 words
A d.c.-coupled video clamping circuit comprising an input terminal , a d.c. signal amplifier having a first input for receiving normal or scrambled video signals coupled to said input terminal; feedback means connected to the output of said signal amplifier, said feedback means including means for detecting the sync tip level of a normal video signal and an error amplifier coupled to the output of said detecting means for producing an error signal representative of variations in the sync tip level from a desired reference level; and control means effective when in a first condition, when it is desired to receive a normal video signal, to apply said error signal to a second input of said signal amplifier, and effective when in a second condition, when it is desired to receive a scrambled video signal, to connect a reference voltage to said second input of said signal amplifier.
Claim 3
Dependent Claim
26 words
The clamping circuit of claim 1, further comprising an impedance buffer interposed between the output of said detecting means and the input of said error amplifier.
Claim 4
Dependent Claim
22 words
The d.c. clamping circuit of claim 1, in which said control means comprises a switch operable between said first and second conditions.
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) | 1990-08-17 | 1991-02-16 | 1991-08-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-17 | 1995-02-16 | 1995-08-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-17 | 1999-02-16 | 1999-08-18 | $7700.00 | Window Closed / Lapsed |