Vehicle alarm system having a vibration-sensitive motion detector
OwnerJames B. Websterinventor
Life of this patent
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Abstract
In a vehicle alarm system there is provided apparatus for producing a digital control signal that defines a command to initiate a timing operation such as an entry delay. The apparatus comprises a transducer, preferably including a piezoelectric device, for generating an electrical waveform that, while the vehicle is undergoing vibration, has an acceleration-representing analog signal component. The apparatus further comprises threshold-setting circuitry responsive to the electrical waveform for causing the initiate-timing command to be given when the acceleration representing signal component exceeds a predetermined threshold.
Claims10
An alarm system for a vehicle which is subject to acceleration and motion which may be induced by tampering or natural causes, said alarm system comprising:
- acceleration sensing means responsive to vehicle acceleration to provide an acceleration signal having an amplitude and frequency which vary with characteristics of the acceleration of the vehicle;
- said acceleration sensing means including a piezo-ceramic device for generating said acceleration signal and a seismic mass coupled to the piezo-ceramic device;
- bandpass filter means for attenuating frequencies of the acceleration signal induced by said natural causes and passing preselected frequencies of the acceleration signal induced by said tampering to provide a filtered acceleration signal, substantially all of said preselected frequencies being less than 40 Hertz;
- first means responsive to the amplitude of the filtered acceleration signal being above a predetermined level for providing an initiate timing signal;
- interval timing means responsive to the initiate timing signal to provide an alarm activation signal;
- and
- means responsive to at least one predetermined condition for inhibiting the interval timing means to prevent the interval timing means from providing the alarm activation signal.
Dependencies are inferred from the claim text.