US3828335A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radio-wave detector for discovering the movement of persons or objects in a confined space
Assignee: Individual
•
Filing: 1973-03-15
•
Granted: 1974-08-06
•
Expires: 1993-03-15
Abstract
Abstract Movements of persons or articles in a monitored space are detected by a change in the effective capacitance between an antenna and an associated counterpoise defining that space, the antenna being energized by an oscillator whose tank circuit is tuned to a predetermined radio frequency f''''e. The oscillator works into a tuned monitoring circuit resonant at a different frequency fo, a capacitive feedback path extending from a tap on the inductive branch of that circuit to an input of the oscillator for applying thereto a control voltage which shifts its operating frequency from f''''e to a value fe closer to fo. This shift in oscillator voltage is reduced by a lowering of the control voltage through a further detuning of the monitoring circuit by a movement to be detected, with resulting change of the operating frequency to a value f''e between f''''e and fe whereby the change in output voltage due to such detuning is intensified. A load circuit connected to the monitoring circuit includes a normally de-energized relay whose energization in response to the aforementioned voltage change produces a voltage drop across a supply resistor common to the relay and the oscillator whereby this voltage change is further stepped up.
Inventors
- 👤 G Salmet
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 20:30
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101; G01V3/102; G08; G08B; G08B13/00; G08B13/22; G08B13/26
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
207 words
A system for detecting movements in a monitored space, comprising: an antenna and a counterpoise therefor jointly defining the space to be monitored; an oscillator provided with a tank circuit tuned to a predetermined radio frequency; a tuned circuit with a resonance frequency differing from said predetermined radio frequency coupled to said oscillator for energization thereby, said tuned circuit being connected between said antenna and said counterpoise whereby said resonance frequency is codetermined by the effective capacitance between said antenna and said counterpoise, said effective capacitance being variable by a movement to be detected in a sense increasing the difference between said resonance frequency and said predetermined frequency; a feedback path between said tuned circuit and said oscillator for delivering to an input of said oscillator a control voltage establishing an operating frequency intermediate said predetermined radio frequency and said resonance frequency to be radiated by said antenna, said control voltage varying with changes in said effective capacitance for shifting said operating frequency toward said predetermined radio frequency in response to a movement to be detected; and a load circuit connected to said tuned circuit, said load circuit including responder means for indicating a voltage change in said tuned circuit due to a movement to be detected.
Claim 2
Independent Claim
207 words
A system for detecting movements in a monitored space, comprising: an antenna and a counterpoise therefor jointly defining the space to be monitored; an oscillator provided with a tank circuit tuned to a predetermined radio frequency; a tuned circuit with a resonance frequency differing from said predetermined radio frequency coupled to said oscillator for energization thereby, said tuned circuit being connected between said antenna and said counterpoise whereby said resonance frequency is codetermined by the effective capacitance between said antenna and said counterpoise, said effective capacitance being variable by a movement to be detected in a sense increasing the difference between said resonance frequency and said predetermined frequency; a feedback path between said tuned circuit and said oscillator for delivering to an input of said oscillator a control voltage establishing an operating frequency intermediate said predetermined radio frequency and said resonance frequency to be radiated by said antenna, said control voltage varying with changes in said effective capacitance for shifting said operating frequency toward said predetermined radio frequency in response to a movement to be detected; and a load circuit connected to said tuned circuit, said load circuit including responder means for indicating a voltage change in said tuned circuit due to a movement to be detected.
Claim 3
Dependent Claim
25 words
A system as defined in claim 1 wherein said load circuit includes a differentiation network of long time constant in series with said responder means.
Claim 4
Dependent Claim
35 words
A system as defined in claim 2, further comprising diode means in said differentiation network for bypassing voltage changes in said tuned circuit of a polarity opposite that due to a movement to be detected.
Claim 5
Dependent Claim
28 words
A system as defined in claim 3 wherein said differentiation network has a resistive branch and a capacitive branch, said diode means being connected across said resistive branch.
Claim 6
Dependent Claim
79 words
A system as defined in claim 2 wherein said responder means includes a normally de-energized relay and trigger means for energizing said relay in response to a significant voltage reduction in said tuned circuit due to a movement to be detected, said relay and said oscillator being provided with a common direct-current supply, further comprising resistance means in series with said common supply for generating a voltage drop upon energization of said relay to intensify said significant voltage reduction.
Claim 7
Dependent Claim
72 words
A system as defined in claim 5 wherein said differentiation network includes a capacitor and a resistor, said load circuit further comprising a rectifying connection and an integrating network inserted between said tuned circuit and said capacitor for charging the latter upon occurrence of said significant voltage reduction, said resistor enabling delayed discharging of said capacitor upon restoration of said effective capacitance to normal whereby said relay remains energized beyond said restoration.
Claim 8
Dependent Claim
35 words
A system as defined in claim 6, further comprising a source of temporary holding voltage for said trigger means and activating means controlled by said relay for making said source operative over a limited period.
Claim 9
Dependent Claim
37 words
A system as defined in claim 7 wherein said source comprises a recording medium carrying a message to be announced and circuitry for deriving said holding voltage from message signals in the output of said recording means.
Claim 10
Dependent Claim
46 words
A system as defined in claim 1 wherein said feedback path is connected to said tuned circuit at a point whose alternating voltage decreases upon variation of said effective capacitance by a movement to be detected, thereby diminishing said control voltage in response to such movement.
Claim 11
Dependent Claim
50 words
A system as defined in claim 9 wherein said oscillator comprises a transistor with a base lead connected to said tank circuit for receiving a reGenerative feedback voltage therefrom, said feedback path including a reactance connected to said base lead for superimposing said control voltage upon said regenerative feedback voltage.
Claim 12
Dependent Claim
28 words
A system as defined in claim 7 wherein said relay is provided with contact means for delivering to said trigger means a holding voltage maintaining said relay energized.
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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) | 1977-08-05 | 1978-02-04 | 1978-08-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-05 | 1982-02-04 | 1982-08-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-05 | 1986-02-04 | 1986-08-06 | $7700.00 | Window Closed / Lapsed |