Back to results
US 4,232,288 AGranted
Vehicle alarm
OwnerRaymond J. Mastermaninventor
Life of this patent
Estimating the term…
Abstract
Method and apparatus for detecting theft or tampering with a vehicle. The method includes monitoring the impedance of individual circuit elements within the electrical system and triggering an alarm whenever the impedance of a circuit element exceeds or falls below predetermined threshold levels. The apparatus includes a transistor switching circuit coupled through diode bridges to individual circuit elements of the vehicle's electrical system.
Claims9
A vehicle alarm system comprising:
- an alarm;
- means for coupling a first vehicle accessory to said alarm for triggering said alarm whenever the magnitude of the impedance from said first vehicle accessory to vehicle ground is greater than a first predetermined threshold level;
- means for coupling a second vehicle accessory to said alarm for triggering said alarm whenever the magnitude of the impedance from said second vehicle accessory to vehicle ground is less than a second predetermined threshold level;
- and
- means for coupling said alarm to a vehicle battery for triggering said alarm whenever said vehicle battery is electrically disconnected from said alarm.
2 more elements
A method for detecting vehicle theft or tampering comprising the steps of:
- monitoring the impedance from a first vehicle accessory to vehicle ground by passing a current from an alarm battery through the first vehicle accessory;
- triggering an alarm whenever the impedance from the first vehicle accessory to vehicle ground is greater than a first predetermined threshold level;
- monitoring the impedance from a second vehicle accessory to vehicle ground;
- and
- triggering an alarm whenever the impedance from the second vehicle accessory to ground is less than a second predetermined threshold.
2 more elements
A vehicle alarm system comprising:
- a switching circuit for activating an alarm relay having first, second and third control inputs and an output;
- an alarm relay having a control input and a first switch output, said control input coupled to said switching circuit output and said first switch output for coupling to an alarm;
- and
- a biased diode bridge coupled to said first control input of said switching circuit and for coupling to a vehicle accessory normally coupled to vehicle ground;
- said second control input of said switching circuit for coupling to a vehicle accessory that is grounded only when the vehicle is operating;
- said third control input for coupling to the vehicle's battery;
- said switching circuit biased such that it will be triggered and in turn trigger said alarm relay whenever the impedance between said biased diode bridge, through a vehicle accessory to vehicle ground is greater than a first predetermined threshold level, said switching circuit also biased to switch and trigger said alarm whenever the impedance between said second control input and vehicle ground drops below a second predetermined threshold level, said switching circuit also biased to be triggered whenever said third control input is disconnected from the vehicle battery.
4 more elements
Dependencies are inferred from the claim text.