Alarm system
OwnerWilliam Nevil Heaton Johnson, Christopher George Rice +1inventors
InventorsWilliam Nevil Heaton Johnson, Christopher George Rice, Steven Hughes
Life of this patent
Estimating the term…
Abstract
An alarm system for detecting attempted theft of an article includes means incorporated in the article itself and arranged to transmit and to continuing transmitting an alarm signal when the article is removed from its original location. An example of the alarm system provides an audible alarm, or transmitted alarm, and is arranged to be operated when a thief removes or attempts to remove a car radio, cassette player, compact disc player or the like from a car. Unauthorized removal of the unit from a car is detected by the consequent breaking of an electrical circuit which may be the power supply connections to the radio from the car electrical system or may be the connections to the loudspeakers or the radio aerial.
Claims6
An alarm system for detecting attempted theft of an article, said alarm system including means incorporated in the article itself and arranged to transmit and to continue transmitting an alarm signal when the article is removed from an original location thereof, or disturbed, said alarm system including a generator so arranged that, when triggered, said generator generates an audible alarm signal at random or pseudo-random intervals or produces a random or pseudo-random pattern of longer and shorter bursts of alarm signal arranged to occur at different time intervals, said generator including a sounder device having a chamber including a cap receiving a piezo-electric disc of a diaphragm forming at least part of a chamber wall of said chamber, said cap having a wall provided with an aperture arranged for the passage of sound waves between a baffle outside said chamber and opposing said aperture, said baffle including a plate spaced by a structure extending between said plate and said cap wall by a small gap defining with said cap wall a peripherally open space radially from the region of said aperture, and a battery for powering said generator, the alarm system being such that said intervals become longer as said battery becomes progressively discharged.
An alarm system for detecting attempted theft of an article, said alarm system including an alarm in such an article triggered in attempted theft of the article;
- and alarm signal generator responsive to said alarm for generating an audible alarm signal at random or pseudo-random intervals or producing a random or pseudo-random pattern of longer and shorter bursts of alarm signal arranged to occur at different time intervals, said alarm signal generator includes a sounder device having a chamber including a cap receiving a piezo-electric disc of a diaphragm, said diaphragm forming at least part of a chamber wall of said chamber, said cap having a cap wall provided with an aperture arranged for the passage of sound waves between a baffle outside said chamber and opposing said aperture, said baffle including a plate spaced by a structure extending between said plate and said cap wall by a small gap defining with said cap wall a peripherally open space radially from the region of said aperture, and a battery for powering said alarm signal generator such that said intervals become longer as said battery becomes progressively discharged.
Dependencies are inferred from the claim text.