US3824532A
Expired / Lapsed
US
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Seismic signal intrusion detection classification system
Assignee: United States Department of the Air Force
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Filing: 1971-09-27
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Granted: 1974-07-16
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Expires: 1991-09-27
Abstract
Abstract An intrusion detection system for detecting and classifying intrusions into a protected area by recognizing their characteristic patterns of seismic disturbances. A sensor produces an electrical signal representative of seismic disturbances created by an intrusion. Signals that surpass a predetermined level constitute an event. These signals are introduced to a histogram circuit that operates to determine the time between these events and to transmit a pulse to a classifier indicating each such time. The classifier generates a plurality of analogue signals each of which individually represents by its amplitude the sum of the pulses falling within a particular time between events pattern. Each pattern is characteristic of a particular type of intrusion such as aircraft, ground vehicle, human, nuisance, etc.
Inventors
- 👤 A Vandierendonck
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 04:40
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/16; G08B13/1654; G08B13/1663; G01; G01V; G01V1/00; G01V1/001; Y; Y10; Y10S; Y10S367/00; Y10S367/901
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
277 words
Apparatus for distinguishing a plurality of physical disturbances having characteristic vibration patterns through a time analysis of said patterns comprising: a sensor for generating a voltage signal representative of a vibration; a level detector for receiving said voltage signal, said level detector being responsive to each said voltage signal exceeding a prescribed threshold for generating a plurality of first pulses; a one shot pulse generator for generating a plurality of second pulses each having a predetermined duration in response to said first pulses frOm said level detector; a clock connected to receive said second pulses, said clock being inhibited from operating throughout the duration of said second pulses; a shift register having a plurality of stages, said shift register being connected to said clock for shifting through said plurality of stages in response to the operation of said clock; said shift register also being connected to receive said second pulses for producing an output signal from one of said plurality of stages into which said register shifted prior to said second pulses, said register being further responsive to said second pulses for resetting at an initial stage in said plurality of stages in preparation for a succeeding one of said second pulses, thereby enabling said register to discern the time between each of said second pulses and a succeeding one of said second pulses; and a classifier connected to said shift register and including a plurality of summing integrators and supervisory means connected to receive the outputs thereof, each summing integrator including weighting resistors connected to individual stages of said register whereby an output signal from a stage may be made of different effect in different integrators.
Claim 2
Dependent Claim
277 words
Apparatus for distinguishing a plurality of physical disturbances having characteristic vibration patterns through a time analysis of said patterns comprising: a sensor for generating a voltage signal representative of a vibration; a level detector for receiving said voltage signal, said level detector being responsive to each said voltage signal exceeding a prescribed threshold for generating a plurality of first pulses; a one shot pulse generator for generating a plurality of second pulses each having a predetermined duration in response to said first pulses frOm said level detector; a clock connected to receive said second pulses, said clock being inhibited from operating throughout the duration of said second pulses; a shift register having a plurality of stages, said shift register being connected to said clock for shifting through said plurality of stages in response to the operation of said clock; said shift register also being connected to receive said second pulses for producing an output signal from one of said plurality of stages into which said register shifted prior to said second pulses, said register being further responsive to said second pulses for resetting at an initial stage in said plurality of stages in preparation for a succeeding one of said second pulses, thereby enabling said register to discern the time between each of said second pulses and a succeeding one of said second pulses; and a classifier connected to said shift register and including a plurality of summing integrators and supervisory means connected to receive the outputs thereof, each summing integrator including weighting resistors connected to individual stages of said register whereby an output signal from a stage may be made of different effect in different integrators.
Claim 3
Dependent Claim
16 words
The apparatus of claim 1 and a rectifier connected between said sensor and said level detector.
Claim 4
Dependent Claim
81 words
The apparatus of claim 2 and an adaptive level detector connected between said rectifier and said level detector comprising: a filter for smoothing the envelope of said voltage signal; a peak detector for detecting the peak amplitude of said voltage signal from said filter; a variable limiter for producing at least one voltage level as a function of said peak amplitude; and a comparator for comparing said voltage signal to said voltage level, said comparator being connected to said level detector.
Claim 5
Dependent Claim
75 words
The apparatus of claim 1 and a time-between-zero-crossings histogram circuit connected to receive said voltage signal from said sensor, said time-between-zero-crossings histrogram circuit being responsive to each positive zero value crossing by said voltage signal for transmitting a second output signal to said classifier indicating the time between each said zero value crossing and a successive zero value crossing by said voltage signal, thereby enabling said classifier to discern the frequency of said voltage signal.
Claim 6
Dependent Claim
130 words
The apparatus of claim 2 and a threshold detector responsive to the output of said rectifier comprising: a first RC filter connected to produce a first signal in response to said voltage signal from said rectifier, said first RC filter having a set time constant; a second RC filter connected to produce a second signal in response to said voltage signal from said rectifier, said second RC filter having a time constant different to the time constant of said first RC filter; first means for comparing said first and second signals, said first means being operative to produce a third signal indicative of the difference between said first and second signals; and second means for initiating power to said apparatus in response to said third signal exceeding a predetermined value.
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) | 1977-07-15 | 1978-01-14 | 1978-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-15 | 1982-01-14 | 1982-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-15 | 1986-01-14 | 1986-07-16 | $7700.00 | Window Closed / Lapsed |