Time multiplexed, false alarm resistant magnetically actuated security system

Claim 1

A system for detecting a relative placement of moveable and fixed members of a barrier outside of a spatial window defined by minimum and maximum allowable distances between the moveable and fixed members, comprising: a magnetic field source to provide a multi-directional proximal magnetic field; multiple determinably selectable magnetic field sensors producing output signals responsive to the proximal magnetic field; and a sensor output signal responsive electrical circuit capable of selecting fewer than all of the determinably selectable sensors at a time and adaptable to selectively establish first and second retainable sensor output signal levels corresponding to the respective minimum and maximum allowable distances between the moveable and fixed members that define the spatial window outside of which relative placement of the moveable and fixed barrier members enables the sensor output signal responsive electrical circuit to notify a monitoring system.

Claim 2

A system for detecting a relative placement of moveable and fixed members of a barrier outside of a spatial window defined by minimum and maximum allowable distances between the moveable and fixed members, comprising: a magnetic field source to provide a multi-directional proximal magnetic field; multiple determinably selectable magnetic field sensors producing output signals responsive to the proximal magnetic field; and a sensor output signal responsive electrical circuit capable of selecting fewer than all of the determinably selectable sensors at a time and adaptable to selectively establish first and second retainable sensor output signal levels corresponding to the respective minimum and maximum allowable distances between the moveable and fixed members that define the spatial window outside of which relative placement of the moveable and fixed barrier members enables the sensor output signal responsive electrical circuit to notify a monitoring system.

Claim 8

An apparatus for detecting a change in relative position between moveable and fixed members of a barrier in a physical security system comprising: a magnetic field sensor producing an output signal responsive to a proximal magnetic field; a magnetic field source to provide the proximal magnetic field; and a sensor output electrical circuit for signaling a monitoring system, the sensor output electrical circuit including a digitally initiated magnetic field source that simulates the effect of a change in relative position between the moveable and fixed members on the output signal sufficient to initiate signaling of the monitoring System, thereby to allow the sensor output electrical circuit to be tested without a change in relative position between the moveable and fixed members of the barrier.

Claim 9

An apparatus for detecting a change in relative position between moveable and fixed members of a barrier in a physical security system comprising: a magnetic field sensor producing an output signal responsive to a proximal magnetic field; a magnetic field source to provide the proximal magnetic field; and a sensor output electrical circuit for signaling a monitoring system, the sensor output electrical circuit including a digitally initiated magnetic field source that simulates the effect of a change in relative position between the moveable and fixed members on the output signal sufficient to initiate signaling of the monitoring System, thereby to allow the sensor output electrical circuit to be tested without a change in relative position between the moveable and fixed members of the barrier.

Claim 11

A method of providing a magnetic field-based security system implemented to have an operator transparent, randomly generated magnetic code for detecting a relative placement of a movable member and a fixed member of a barrier, comprising: operatively connecting a randomly coded magnetic field source to one of the movable and fixed members, the randomly coded magnetic field source producing a magnetic field characterized by a magnetic field density pattern; operatively connecting a set of multiple magnetic field sensors to the other one of the movable and fixed members, each of the sensors producing a signal responsive to the magnetic field density pattern; and calibrating the security system by: setting the movable and fixed members at first and second relative positions that correspond to respective first and second distances between the randomly coded magnetic field source and the set of multiple magnetic field sensors, acquiring at each of the first and second positions information corresponding to the signal produced by each of the magnetic field sensors, determining from the acquired information in accordance with an operator-transparent computational procedure threshold level distances between the randomly coded magnetic field source and the set of magnetic field sensors that define an alarm condition so that the nature of the interaction between the random code characterizing the magnetic field source and the set of sensors remains unrevealed to an operator carrying out the method, and storing in memory the threshold level differences for later comparison with an actual distance between the randomly coded magnetic field source and the set of sensors when the system is in use.

Claim 12

A method of providing a magnetic field-based security system implemented to have an operator transparent, randomly generated magnetic code for detecting a relative placement of a movable member and a fixed member of a barrier, comprising: operatively connecting a randomly coded magnetic field source to one of the movable and fixed members, the randomly coded magnetic field source producing a magnetic field characterized by a magnetic field density pattern; operatively connecting a set of multiple magnetic field sensors to the other one of the movable and fixed members, each of the sensors producing a signal responsive to the magnetic field density pattern; and calibrating the security system by: setting the movable and fixed members at first and second relative positions that correspond to respective first and second distances between the randomly coded magnetic field source and the set of multiple magnetic field sensors, acquiring at each of the first and second positions information corresponding to the signal produced by each of the magnetic field sensors, determining from the acquired information in accordance with an operator-transparent computational procedure threshold level distances between the randomly coded magnetic field source and the set of magnetic field sensors that define an alarm condition so that the nature of the interaction between the random code characterizing the magnetic field source and the set of sensors remains unrevealed to an operator carrying out the method, and storing in memory the threshold level differences for later comparison with an actual distance between the randomly coded magnetic field source and the set of sensors when the system is in use.