Patent ID: 7839143

Claim:
A method of detecting a change in a magnetic condition of a vehicle, comprising: a. generating a first time-varying magnetic field component proximate to a first portion of the vehicle at a first location; b. generating at least one second time-varying magnetic field component proximate to at least one second portion of said vehicle at at least one corresponding second location, wherein said at least one corresponding second location is separated from said first location, said first portion of said vehicle and said at least one second portion of said vehicle are at least partially conductive so that said first time-varying magnetic field component generates a corresponding first eddy current component in said first portion of said vehicle, said at least one second time-varying magnetic field component generates a corresponding at least one second eddy current component in said at least one second portion of said vehicle, and said first location and at least one of said at least one corresponding second location are each proximally adjacent to corresponding separate conductive portions of a common surface of said vehicle; and c. detecting a change in the magnetic condition of said vehicle responsive to a first signal responsive to said corresponding first eddy current component, and responsive to at least one second signal responsive to said corresponding at least one second eddy current component.