US4661799A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Loop detector
Assignee: ELECTROMATIC Pty Ltd 28 WIGATHORPE ROAD PIETERMARITZBURG NATAL REPUBLIC OF SOUTH AFRICA
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Filing: 1985-08-23
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Granted: 1987-04-28
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Expires: 2005-08-23
Abstract
Abstract An inductive loop detector which includes a detector which is coupled to the loop by means of a parallel tuned circuit and a receiver which is coupled to the loop by means of a parallel tuned circuit, with the two tuned circuits having different resonant frequencies.
Inventors
- 👤 David A. Buttemer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:39
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101; G08; G08G; G08G1/00; G08G1/01; G08G1/042
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
90 words
A method of operating a loop detector which includes the steps of energizing a loop with a first signal at a first frequency, monitoring the first signal to detect the presence of a vehicle within the electromagnetic area of the loop, and upon so detecting the presence of a vehicle, of transmitting a signal to the vehicle to activate a transmitter on the vehicle, the transmitter transmitting a second signal at a second frequency which is different from the first frequency, and monitoring the loop to detect the second signal.
Claim 2
Independent Claim
90 words
A method of operating a loop detector which includes the steps of energizing a loop with a first signal at a first frequency, monitoring the first signal to detect the presence of a vehicle within the electromagnetic area of the loop, and upon so detecting the presence of a vehicle, of transmitting a signal to the vehicle to activate a transmitter on the vehicle, the transmitter transmitting a second signal at a second frequency which is different from the first frequency, and monitoring the loop to detect the second signal.
Claim 3
Dependent Claim
19 words
A method according to claim 1 which includes the step of maintaining the first frequency within specified frequency limits.
Claim 4
Dependent Claim
14 words
A method according to claim 2 wherein the first frequency is maintained substantially constant.
Claim 5
Dependent Claim
84 words
An inductive loop detector which includes an inductive loop, means for energizing the loop with a first signal at a first frequency, the first frequency being maintained within specified frequency limits, means for monitoring the first signal to detect the presence of a vehicle within the electro-magnetic area of the loop, and receiver means which is responsive to a signal transmitted from a vehicle and detected by the loop, the transmitted signal being at a second frequency which is different from the first frequency.
Claim 6
Dependent Claim
84 words
An inductive loop detector which includes an inductive loop, means for energizing the loop with a first signal at a first frequency, the first frequency being maintained within specified frequency limits, means for monitoring the first signal to detect the presence of a vehicle within the electro-magnetic area of the loop, and receiver means which is responsive to a signal transmitted from a vehicle and detected by the loop, the transmitted signal being at a second frequency which is different from the first frequency.
Claim 7
Dependent Claim
63 words
An inductive loop detector according to claim 4 wherein the loop energizing means includes a first parallel tuned circuit which is resonant at the first frequency and which couples the first signal to the loop, and the receiver means includes a receiver, and a second parallel tuned circuit which is resonant at the second frequency and which couples the receiver to the loop.
References Cited (Backward Citations)
US3891980A
Cited
US3996555A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-04-27 | 1990-10-27 | 1991-04-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-27 | 1994-10-27 | 1995-04-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-27 | 1998-10-27 | 1999-04-28 | $7700.00 | Window Closed / Lapsed |