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Patent US3943503A successfully refreshed from Google Patents.
US3943503A
Expired / Lapsed
US
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Electronic intruder alarm apparatus
Assignee: UNWIN ELECTRONICS Ltd
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Filing: 1974-11-11
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Granted: 1976-03-09
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Expires: 1994-11-11
Abstract
Abstract A radio-frequency source irradiates a space within which an intruder is to be detected, this space being illuminated by fluorescent tubes. Successive peak levels in the returned signals are compared and a fall in the peak amplitude results in a comparator, arranged to compare the peak amplitude with that of a preceding peak, failing to yield a reset signal to a timer circuit. After a time interval just greater than the periodicity of the a.c. supply to the fluorescent tubes the time yields an alarm control signal. If the peak value recovers during this interval the timer is reset and no alarm control signal is generated. The alarm control signals are applied to an integrator yielding alarm signals in response to predetermined repetition of the alarm control signals. The alarm signal is delayed and used to reset the integrator, as well as initiating an alarm condition.
Inventors
- 👤 Jeremy Hugh Whitman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:25
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
221 words
An intruder alarm apparatus including a radio-frequency radiation source for irradiating with said radio-frequency radiation a space within which an intruder is to be detected, a radio detector responsive to said radio-frequency radiation returned towards said source from objects within said space or from the boundaries thereof to develop detector signals representative of the amount of said returned radiation, and signal processing circuit means responsive to said detector signals to develop an alarm signal in response to predetermined fluctuations in said amount of said returned radiation, the improvement comprising: signal peak comparator means in said signal processing circuit means, said signal peak comparator means yielding a resetting signal when the amplitude of a peak in said detector signal is not substantially less than the amplitude of a preceding signal peak; timer means reset to an initial condition by each said resetting signal and, unless so reset, yielding an alarm control signal at an output thereof at the end of a predetermined time interval, the duration of said time interval being somewhat greater than the periodicity of an alternating current supply used to energize fluorescent tubes lighting said space; and alarm means predeterminedly responsive to said alarm control signal to yield an intruder alarm signal; whereby said alarm apparatus is immune to periodically fluctuating return of said radiation from said fluorescent tubes.
Claim 2
Dependent Claim
221 words
An intruder alarm apparatus including a radio-frequency radiation source for irradiating with said radio-frequency radiation a space within which an intruder is to be detected, a radio detector responsive to said radio-frequency radiation returned towards said source from objects within said space or from the boundaries thereof to develop detector signals representative of the amount of said returned radiation, and signal processing circuit means responsive to said detector signals to develop an alarm signal in response to predetermined fluctuations in said amount of said returned radiation, the improvement comprising: signal peak comparator means in said signal processing circuit means, said signal peak comparator means yielding a resetting signal when the amplitude of a peak in said detector signal is not substantially less than the amplitude of a preceding signal peak; timer means reset to an initial condition by each said resetting signal and, unless so reset, yielding an alarm control signal at an output thereof at the end of a predetermined time interval, the duration of said time interval being somewhat greater than the periodicity of an alternating current supply used to energize fluorescent tubes lighting said space; and alarm means predeterminedly responsive to said alarm control signal to yield an intruder alarm signal; whereby said alarm apparatus is immune to periodically fluctuating return of said radiation from said fluorescent tubes.
Claim 3
Dependent Claim
101 words
The invention claimed in claim 1 wherein said signal peak comparator means comprises; first comparator means (44) having first and second inputs and an output, said first comparator means providing said resetting signal at said output only when the potential applied to said first input exceeds that at said second input; circuit means (40) applying said detector signal to said first input of said first comparator means; potential storage means (45), (46) responsive to an applied potential to provide a stored potential which diminishes progressively from said applied potential; and means (47) applying said resetting signal to said potential storage means.
Claim 4
Dependent Claim
62 words
The invention claimed in claim 2 wherein said potential storage means comprises a storage capacitor (45), and a resistor (46) coupling said storage capacitor to said second input of said first comparator means (44), and further wherein said means applying said resetting signal to said potential storage means comprises a diode (47) coupling said first camparator output to charge said storage capacitor.
Claim 5
Dependent Claim
36 words
The invention claimed in claim 3 wherein said alarm control signal is coupled from said timer output by way of the series combination of a resistor (80) and a diode (81) to discharge said storage capacitor.
Claim 6
Dependent Claim
87 words
The invention claimed in claim 1, wherein said timer means comprises a timer capacitor (51), stabilized positive supply means (1), charging means (50) progressively charging said capacitor from said positive supply means to increase the potential thereon, switch means (49) operable by said reset signal to discharge said timer capacitor, and trigger means (53) responsive to the potential on said timer capacitor attaining a predetermined level to yield said alarm control signal, said charging means charging said capacitor to said predetermined level in said predetermined time interval.
Claim 7
Dependent Claim
83 words
The invention claimed in claim 5, wherein said timer capacitor has one grounded terminal, said charging means comprises a charging resistor connected between the other terminal of said capacitor and said stabilized positive supply means, and further wherein said switch means comprises a transistor having a grounded emitter, a collector connected to the junction of said charging resistor with said timing capacitor, and a base coupled by way of a further resistor to said first comparator means to receive said resetting signal therefrom.
Claim 8
Dependent Claim
65 words
The invention claimed in claim 6 wherein said trigger means comprises a difference amplifier (53) of which the inverting input is coupled by way of a resistor (52) to the junction of said timer capacitor with said charging resistor, the non-inverting input is coupled by way of resistance means (54, 55) to said stabilized positive supply and the output is coupled to said alarm means.
Claim 9
Dependent Claim
30 words
The invention claimed in claim 1 wherein said alarm means includes integrator means responsive to predeterminedly repeated application of said alarm control signal thereto to yield an alarm initiating signal.
Claim 10
Dependent Claim
107 words
The invention claimed in claim 8, wherein said integrator means includes an integrator capacitor (60), a stabilized positive supply means (1), switch means (58) operable by said alarm control signal to supply a predetermined current pulse from said stabilized positive supply means to said integrator capacitor, trigger means (62) responsive to a predetermined state of charge in said capacitor to yield said alarm initiating signal, discharge means (68) responsive to an applied signal to discharge said capacitor, and signal delay means (65-67) yielding an output signal predeterminedly delayed with respect to an applied signal, said signal delay means applying said alarm initiating signal to said discharge means.
Claim 11
Dependent Claim
46 words
The invention claimed in claim 9 wherein said switch means comprises a p-n-p transistor of which the emitter is connected to said stabilized positive supply, the collector is connected to said capacitor and the base is coupled to receive said alarm control signal from said timer.
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) | 1979-03-09 | 1979-09-08 | 1980-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-09 | 1983-09-08 | 1984-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-09 | 1987-09-08 | 1988-03-09 | $7700.00 | Window Closed / Lapsed |