US3806907A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Perimeter intrusion detection system with common mode rejection
Assignee: Texas Instruments Inc
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Filing: 1972-03-23
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Granted: 1974-04-23
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Expires: 1992-03-23
Abstract
Abstract A perimeter surveillance system is described for sensing intrusions into a specified area. The system includes a cable buried beneath the surface of the earth and along the perimeter of the area to be protected. Associated with the cable are a plurality of transducers electrically connected thereto and also buried beneath the surface of the earth. These transducers may be, for example, piezoelectric elements sensitive to soil stress in substantially one direction only and may be mounted in an arrowhead-shaped housing for ease of installation. Each piezoelectric transducer is connected to the buried cable with its polarity opposite to that of its nearest neighbors in order to cancel out undesired noise from remote sources. The transducers themselves are capable of broad-band response, from just above d.c. to several kHz. In one embodiment, the response of the total system is limited to sub-seismic frequencies, so that the system is not sensitive to seismic-band signals caused by wind, rain, hail, distant vehicular traffic, vibrating machinery and other remote natural and man-made disturbances.
Inventors
- 👤 L Bound
- 👤 A Hunting
- 👤 P Linden
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 20:17
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/02; G08B13/10
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
180 words
A perimeter intrusion detection system for sensing intrusions across a perimeter comprising: a. at least one segment of cable to be buried beneath the surface of the earth including a pair of electrical conductors; b. a plurality of soil stress sensors each comprising a transducer selectively responsive to pressure to be buried in a spaced relation one to another for selective activation by a lateral pressure force, each oF said sensors having positive and negative terminals electrically interconnected with said pair of electrical conductors of the cable segment with a polarity opposite to that of an adjacent sensor, whereby when a noise stress activates adjoining sensors to substantially equal degrees the output of one sensor opposes the output of the adjacent sensor to alleviate false alarms, and when a sufficiently large localized pressure force activates essentially only one sensor an electrical signal representative of the pressure force is produced; and c. an electrical signal indicating means positioned remotely to said sensors and operatively responsive to the electrical signal representative of the pressure force to indicate the presence of an intrusion.
Claim 2
Dependent Claim
180 words
A perimeter intrusion detection system for sensing intrusions across a perimeter comprising: a. at least one segment of cable to be buried beneath the surface of the earth including a pair of electrical conductors; b. a plurality of soil stress sensors each comprising a transducer selectively responsive to pressure to be buried in a spaced relation one to another for selective activation by a lateral pressure force, each oF said sensors having positive and negative terminals electrically interconnected with said pair of electrical conductors of the cable segment with a polarity opposite to that of an adjacent sensor, whereby when a noise stress activates adjoining sensors to substantially equal degrees the output of one sensor opposes the output of the adjacent sensor to alleviate false alarms, and when a sufficiently large localized pressure force activates essentially only one sensor an electrical signal representative of the pressure force is produced; and c. an electrical signal indicating means positioned remotely to said sensors and operatively responsive to the electrical signal representative of the pressure force to indicate the presence of an intrusion.
Claim 3
Dependent Claim
31 words
The system of claim 1 wherein all the soil stress sensors are implanted in the earth at approximately the same depth and all face the same direction along said cable segment.
Claim 4
Dependent Claim
32 words
The system of claim 1 wherein each of the plurality of soil stress sensors along said cable segment is connected in parallel to the pair of electrical conductors of the cable segment.
Claim 5
Dependent Claim
23 words
The system of claim 1 wherein the plurality of soil stress sensors are oriented in a vertical plane perpendicular to said cable segment.
Claim 6
Dependent Claim
19 words
The system of claim 1 wherein said plurality of spaced soil stress sensors are located within said cable segment.
Claim 7
Dependent Claim
42 words
The system of claim 1 wherein each soil stress sensor is oriented in a substantially vertical plane perpendicular to the at least one cable segment whereby said soil stress sensor is operatively responsive to soil stress variations in substantially only one direction.
Claim 8
Dependent Claim
20 words
The system of claim 1, wherein the spacing between said plurality of soil stress sensors is less than 8 feet.
References Cited (Backward Citations)
US2548990A
Cited
US2836737A
Cited
US3109165A
Cited
US3479536A
Cited
US3613061A
Cited
US3688251A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-22 | 1977-10-22 | 1978-04-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-22 | 1981-10-22 | 1982-04-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-22 | 1985-10-22 | 1986-04-23 | $7700.00 | Window Closed / Lapsed |