Patent US3755627A successfully refreshed from Google Patents.
Patent US4680574A successfully refreshed from Google Patents.
US4680574A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Appliance anti-theft circuitry
Assignee: Individual
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Filing: 1985-03-22
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Granted: 1987-07-14
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Expires: 2005-03-22
Abstract
Abstract The invention utilizes time domain reflectrometry to obtain a measure of the length of wire connecting an electrical appliance to its power distribution panel. An unauthorized change in this length is interpreted as an attempt to steal the appliance. Coded disabling keys are provided to allow an authorized user to unplug and move the appliance. The invention can be mounted within the appliance, requires no modification of the existing wiring or receptacles and is unaffected by power failures.
Inventors
- 👤 Bryan J. Ruffner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:25
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/02; G08B13/14; G08B13/1409
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
132 words
An alarm device for detecting the removal of an electrical apparatus when plugged into a three-terminal power-supply outlet having a hot terminal and electrically interconnected neutral and grounded terminals where said alarm device comprises: circuitry for cyclically applying a voltage across said neutral and grounded terminals; circuitry for timing the return of an inverted electrical reflection of said applied voltage caused by the point of interconnection of said interconnected neutral and grounded terminals; circuitry for electrically storing the measured time of said inverted electrical reflection; circuitry for comparing a stored value of said measured time with subsequent values of said measured time; and circuitry for generating an alarm signal when a stored value of said measured time and a subsequent value of said measured time differ by more than a predetermined amount.
Claim 2
Dependent Claim
132 words
An alarm device for detecting the removal of an electrical apparatus when plugged into a three-terminal power-supply outlet having a hot terminal and electrically interconnected neutral and grounded terminals where said alarm device comprises: circuitry for cyclically applying a voltage across said neutral and grounded terminals; circuitry for timing the return of an inverted electrical reflection of said applied voltage caused by the point of interconnection of said interconnected neutral and grounded terminals; circuitry for electrically storing the measured time of said inverted electrical reflection; circuitry for comparing a stored value of said measured time with subsequent values of said measured time; and circuitry for generating an alarm signal when a stored value of said measured time and a subsequent value of said measured time differ by more than a predetermined amount.
Claim 3
Dependent Claim
18 words
The alarm device of claim 1 further comprising circuitry for generating a code to disable said alarm signal.
Claim 4
Dependent Claim
27 words
The alarm device of claims 1 or 2 further comprising circuitry for converting the energy from said power supplying into a form usable by said alarm device.
Claim 5
Dependent Claim
29 words
The alarm device of claim 3 further comprising a battery and circuitry for providing energy usable by said alarm device in the absence of energy from said power supply.
Claim 6
Independent Claim
159 words
The method of detecting changes in the distance of an electrical apparatus from its power distribution panel when said panel is wired with a standard hot, neutral and grounded wire arrangement with said neutral and grounded wires shorted together at said panel so as to present a continuous low impedance loop at the terminals of said apparatus where said method comprises: the repetitious transmitting of a voltage pulse over the transmission line formed by said neutral and grounded wires; the timing of the return of an inverted electrical reflection of said voltage pulse caused by said short at said panel; the electrical storing of the measured time of said inverted electrical reflection; the comparing of a stored value of said measured time with subsequent values of said measured time; and the generating of an alarm signal when a stored value of said measured time and a subsequent value of said measured time differ by more than a predetermined amount.
Claim 7
Independent Claim
159 words
The method of detecting changes in the distance of an electrical apparatus from its power distribution panel when said panel is wired with a standard hot, neutral and grounded wire arrangement with said neutral and grounded wires shorted together at said panel so as to present a continuous low impedance loop at the terminals of said apparatus where said method comprises: the repetitious transmitting of a voltage pulse over the transmission line formed by said neutral and grounded wires; the timing of the return of an inverted electrical reflection of said voltage pulse caused by said short at said panel; the electrical storing of the measured time of said inverted electrical reflection; the comparing of a stored value of said measured time with subsequent values of said measured time; and the generating of an alarm signal when a stored value of said measured time and a subsequent value of said measured time differ by more than a predetermined amount.
Claim 8
Dependent Claim
17 words
The method of claim 5 further comprising the generating of a code to disable said alarm signal.
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) | 1990-07-13 | 1991-01-12 | 1991-07-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-07-13 | 1995-01-12 | 1995-07-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-07-13 | 1999-01-12 | 1999-07-14 | $7700.00 | Window Closed / Lapsed |