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US4742338A
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Intruder alarm system
Assignee: BAE Systems Electronics Ltd
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Filing: 1986-05-19
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Granted: 1988-05-03
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Expires: 2006-05-19
Abstract
Abstract An intruder alarm system of the type used to detect mechanical vibrations in a security fence or the like. Vibrations are assessed for alarm potential by detecting peak amplitudes against a dynamic vibration reference. A sufficient ratio between the two indicates an intrusion.
Inventors
- 👤 Roy Baxendale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:09
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/02; G08B13/12; G08B13/122; G08B13/16; G08B13/1654
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
113 words
An intruder alarm system comprising: at least one electromechanical transducer for providing electric signals having an amplitude in response to vibrations incident thereon; envelope detector means for deriving a unidirectional waveform signal representing the amplitude of said electric signals; integrating circuit means for deriving a dynamic reference signal from said unidirectional waveform signal; comparator means for comparing said unidirectional waveform signal with said dynamic reference signal; means responsive to an output signal from said comparator means for generating an alarm indication; and means for providing a discharge path between said integrating circuit means and an output of said envelope detector means for preventing said dynamic reference signal from exceeding said unidirectional waveform signal.
Claim 2
Dependent Claim
113 words
An intruder alarm system comprising: at least one electromechanical transducer for providing electric signals having an amplitude in response to vibrations incident thereon; envelope detector means for deriving a unidirectional waveform signal representing the amplitude of said electric signals; integrating circuit means for deriving a dynamic reference signal from said unidirectional waveform signal; comparator means for comparing said unidirectional waveform signal with said dynamic reference signal; means responsive to an output signal from said comparator means for generating an alarm indication; and means for providing a discharge path between said integrating circuit means and an output of said envelope detector means for preventing said dynamic reference signal from exceeding said unidirectional waveform signal.
Claim 3
Dependent Claim
38 words
The intruder alarm system according to claim 1, wherein said comparator means is operative for generating said output signal whenever said unidirectional waveform signal compared to said dynamic reference signal form a ratio which exceeds a predetermined value.
Claim 4
Dependent Claim
17 words
The intruder alarm system according to claim 2, wherein said predetermined value is between 3 and 4.5.
Claim 5
Dependent Claim
15 words
The intruder alarm system according to claim 3, wherein said predetermined value is approximately 3.5.
Claim 6
Dependent Claim
32 words
The intruder alarm system according to claim 1, wherein said envelope detector means includes integrating means having a rapid rise time and a decay time which is between 0.3 and 1.0 seconds.
Claim 7
Dependent Claim
44 words
The intruder alarm system according to claim 2, and means for applying a low-level d.c. voltage to an output of said envelope detector means so that said signals applied to said comparator means tend to equalize when the amplitude of said vibrations is low.
Claim 8
Dependent Claim
31 words
The intruder alarm system according to claim 1, and further detector means for detecting large fluctuations in the electric signals provided by said transducer, and for triggering an alarm signal accordingly.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-05-03 | 1991-11-02 | 1992-05-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-03 | 1995-11-02 | 1996-05-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-03 | 1999-11-02 | 2000-05-03 | $7700.00 | Window Closed / Lapsed |