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US3631442A
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Anti-shoplifting system
Assignee: Individual
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Filing: 1968-03-22
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Granted: 1971-12-28
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Expires: 1988-03-22
Abstract
Abstract Article theft detection system wherein a passive nonlinear radio transponder is attached to each article to be protected, and an exit way is monitored by a loop antenna which is energized by currents of two different frequencies. The transponders radiate the difference frequency when subjected to a field of the two energizing frequencies. Receiving means connected to the loop antenna detects signals having a frequency equal to the difference between the two energizing frequencies, and actuates an alarm.
Inventors
- 👤 Robert E Fearon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 07:34
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G01; G01S; G01S13/00; G01S13/74; G01S13/75; G01S13/751; G01S13/753; G06; G06K; G06K7/00; G06K7/10; G06K7/10009; G08B13/2428; G08B13/2431; G08B13/2437; G08B13/2442; G08B13/2465; G08B13/2468; G08B13/2474
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
99 words
A system for sensing passage of objects through a surveillance area and useful for detecting theft of an object from an area, comprising: means proximate the area for concurrently producing at least two oscillating electromagnetic energy components of different frequency in the area; an electromagnetically nonlinear marker associated with each object for reradiating electromagnetic energy at frequencies equal to sums and differences of the frequencies of said components when said components are coupled to the marker; and means for sensing electromagnetic energy in said area and for producing a signal in response to sensing energy reradiated by a marker.
Claim 2
Independent Claim
99 words
A system for sensing passage of objects through a surveillance area and useful for detecting theft of an object from an area, comprising: means proximate the area for concurrently producing at least two oscillating electromagnetic energy components of different frequency in the area; an electromagnetically nonlinear marker associated with each object for reradiating electromagnetic energy at frequencies equal to sums and differences of the frequencies of said components when said components are coupled to the marker; and means for sensing electromagnetic energy in said area and for producing a signal in response to sensing energy reradiated by a marker.
Claim 3
Dependent Claim
75 words
A system according to claim 1 wherein said energy component producing means comprises at least two emitting means each of which produces a said energy component and each of which comprises a combination of a coil winding and a capacitor, which combination is resonant at the frequency at which the emitting means produces its said energy component and wherein each emitting means receives no energy from any other emitting means concurrently producing an energy component.
Claim 4
Dependent Claim
19 words
A system according to claim 2 wherein said emitting means which produce energy components concurrently have no mutual inductance.
Claim 5
Dependent Claim
56 words
A system according to claim 2 wherein each said emitting means further comprises a filter coupled in electrical series with said combination, which filter has a narrow passband centered about the resonant frequency of said combination to prevent energy from any other concurrently producing emitting means from being received by the emitting means of said combination.
Claim 6
Dependent Claim
40 words
A system according to claim 2 further comprising a deactivating device for producing a recognizable change in a merchandise marker to permit deactivation of the marker of a good the removal of which from the designated area has been authorized.
References Cited (Backward Citations)
FR763681A
Cited
US2193102A
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US2774060A
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US3098971A
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US3218638A
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US3384892A
Cited
US3493955A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-27 | 1975-06-28 | 1975-12-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-27 | 1979-06-28 | 1979-12-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-27 | 1983-06-28 | 1983-12-28 | $7700.00 | Window Closed / Lapsed |