US3877002A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intrusion detecting system
Assignee: SOUTHWEST MICROWAVE Inc A CORP OF
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Filing: 1973-05-25
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Granted: 1975-04-08
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Expires: 1993-05-25
Abstract
Abstract An intrusion detecting system including a transmitting unit for radiating microwave energy along a preselected path which is amplitude modulated at a preselected frequency, and a receiving unit positioned on the path and separated from the transmitting unit for receiving a portion of the radiated microwave energy which includes a signal processing circuit which distinguishes between radiated signals which are amplitude modulated at said preselected frequency and other radiated signals and which provide an output signal to an alarm device or the like when the received portion of the radiated microwave energy is additionally amplitude modulated in a manner characteristic of an intrusion. The signal processing circuit includes a dual rate automatic gain control which responds to increases in the receiving unit signals at a fast rate and responds to decreases in the receiving unit signals at a second substantially slower rate.
Inventors
- 👤 James Cheal
- 👤 Larry Eccleston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 06:56
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
231 words
An intrusion detecting system for detecting the entrance of an intruder into a zone of protection comprising: transmitting means for radiating high frequency energy; receiving means for receiving at least a portion of said radiated high frequency energy including amplifying means for receiving a signal representative of said received portion of said radiated high frequency energy and for providing an output signal, said amplifying means having automatic gain control means for decreasing the gain in response to increases in said received signal at a first rate to maintain said output signal substantially constant and for increasing the gain in response to decreases in said received signal at a second rate to maintain said output signal substantially constant, said first rate being selected to be greater than the rate of increase of said received signal upon the approach of said intruder to said zone of protection, said second rate being selected to be substantially less than said first rate and to be less than the rate of decrease of said received signal upon the entrance of said intruder into said zone of protection so that the response of said receiving means to an intrusion is enhanced by the response of said gain control means to the increase in said received signal upon approach of said intruder to said zone of protection; and means responsive to said output signal for indicating an intrusion.
Claim 2
Dependent Claim
231 words
An intrusion detecting system for detecting the entrance of an intruder into a zone of protection comprising: transmitting means for radiating high frequency energy; receiving means for receiving at least a portion of said radiated high frequency energy including amplifying means for receiving a signal representative of said received portion of said radiated high frequency energy and for providing an output signal, said amplifying means having automatic gain control means for decreasing the gain in response to increases in said received signal at a first rate to maintain said output signal substantially constant and for increasing the gain in response to decreases in said received signal at a second rate to maintain said output signal substantially constant, said first rate being selected to be greater than the rate of increase of said received signal upon the approach of said intruder to said zone of protection, said second rate being selected to be substantially less than said first rate and to be less than the rate of decrease of said received signal upon the entrance of said intruder into said zone of protection so that the response of said receiving means to an intrusion is enhanced by the response of said gain control means to the increase in said received signal upon approach of said intruder to said zone of protection; and means responsive to said output signal for indicating an intrusion.
Claim 3
Dependent Claim
26 words
An intrusion detecting system according to claim 1 wherein said received signal represents changes in the amount of said received portion of said high frequency energy.
Claim 4
Dependent Claim
19 words
An intrusion detecting system according to claim 1 wherein said first rate is approximately ten times said second rate.
Claim 5
Dependent Claim
40 words
An intrusion detecting system according to claim 1 wherein said transmitting means and said receiving means are at spaced locations so that an intrusion intermediate said spaced locations causes a change in said received portion of said high frequency energy.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-07 | 1978-10-07 | 1979-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-07 | 1982-10-07 | 1983-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-07 | 1986-10-07 | 1987-04-08 | $7700.00 | Window Closed / Lapsed |