US3745552A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intrusion signature detector requiring both frequency and amplitude shifts
Assignee: TDY Industries LLC
•
Filing: 1971-09-13
•
Granted: 1973-07-10
•
Expires: 1991-09-13
Abstract
Abstract An intrusion detector system which uses a geophone to sense both ambient environmental events and man-made cultural events, the system being responsive to the combination of changes both in the amplitude and in the frequency of the waveform signature picked up by the geophone to detect intrusions characterized by man-made events superimposed upon ambient events. An AM detector channel responds to changes in amplitude of the geophone output waveform, and an FM discriminator channel responds to shifts in its momentary frequency, these latter shifts being stored both in a long-term integrator and in a short-term integrator whose contents are continuously compared to determine when short-term conditions begin changing as compared with averaged long-term conditions, the latter representing mainly environmental noise. When at the same time both channels respond beyond certain preset threshold levels the system delivers outputs, and these outputs can either directly set off alarms or else a certain number of outputs can be counted before an alarm results thereby tending to reduce the liklihood of false alarms.
Inventors
- 👤 M Wilt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:41
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/16; G08B13/1654; G08B13/1663
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
291 words
In a system for detecting an intrusion into an area wherein both ambient noises and man-made noises are picked up by vibration transducer means and converted into electrical input signals including a spectrum of components representing the frequencies of said noises, the combination of: a. AGC amplifier means connected to said transducer means and having a time constant which is long as compared with the period of the lowest input frequency to which the transducer means is responsive; b. an AM signal channel connected to said amplifier means to receive amplified input signals and including means for detecting their amplitude levels, low-pass filter means coupled to receive the output of the detecting means and pass only frequencies below an arbitrarily selected highest man-made noise frequency, and threshold means connected to receive said filtered components and operative to deliver a first output each time the level of those components exceeds a preset amplitude level; c. an FM signal channel connected to said amplifier means to receive amplified input signals and including FM discriminator means operative to deliver an analog potential whose level represents the dominant frequency component of the input signal, separate long-term and short-term integrator means both connected to the FM discriminator means to receive said analog potential and respectively delivering a long-term integrated level and a short-term integrated level, comparator means having separate inputs connected to the respective integrator means to receive said levels, the comparator means being responsive to a preset differential when present between said levels to deliver a second output; and d. AND gate means connected to receive said first and second outputs and responsive to the presence at the same time of both the first and the second output for delivering a signal indicating an intrusion.
Claim 2
Dependent Claim
291 words
In a system for detecting an intrusion into an area wherein both ambient noises and man-made noises are picked up by vibration transducer means and converted into electrical input signals including a spectrum of components representing the frequencies of said noises, the combination of: a. AGC amplifier means connected to said transducer means and having a time constant which is long as compared with the period of the lowest input frequency to which the transducer means is responsive; b. an AM signal channel connected to said amplifier means to receive amplified input signals and including means for detecting their amplitude levels, low-pass filter means coupled to receive the output of the detecting means and pass only frequencies below an arbitrarily selected highest man-made noise frequency, and threshold means connected to receive said filtered components and operative to deliver a first output each time the level of those components exceeds a preset amplitude level; c. an FM signal channel connected to said amplifier means to receive amplified input signals and including FM discriminator means operative to deliver an analog potential whose level represents the dominant frequency component of the input signal, separate long-term and short-term integrator means both connected to the FM discriminator means to receive said analog potential and respectively delivering a long-term integrated level and a short-term integrated level, comparator means having separate inputs connected to the respective integrator means to receive said levels, the comparator means being responsive to a preset differential when present between said levels to deliver a second output; and d. AND gate means connected to receive said first and second outputs and responsive to the presence at the same time of both the first and the second output for delivering a signal indicating an intrusion.
Claim 3
Dependent Claim
59 words
In a combination as set forth in claim 1, delay means interposed in the AM signal channel for delaying its output by an amount of time substantially equal to the integrating time of the short-term integrator means, thereby to bring the outputs of the AM and FM channels into time coincidence when caused by the same input signal event.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |