Patent ID: 8552838

Claim:
A passive wireless system for monitoring a protected area comprising: a plurality of passive sensors deployed throughout the protected area, each of the plurality of passive sensors operable to detect a respective security event at a location of the passive sensor within the protected area; a reader that receives signals from the plurality of passive sensors; a plurality of exciters disposed at respective known locations throughout the protected area, each of the plurality of exciters transmitting a radio frequency pulse at a variable time interval that powers at least one passive sensor of the plurality of passive sensors; and a controller that separately controls each of the plurality of exciters to transmit the radio frequency pulse at the variable time interval and that detects responses through the reader from sensors located near and that are powered by the radio frequency pulse of the transmitting exciter, wherein each of the plurality of exciters has a different variable transmission interval such that there is no signal interference among the plurality of exciters and wherein by varying the time interval and controlling each of the exciters separately, the controller identifies the location of the at least one passive sensor which transmitted a signal in response to the transmitted radio frequency pulse based upon the known location of the transmitting exciter wherein the controller selects the variable time interval of at least some of the plurality of passive sensors depending on a status of said passive wireless security system, said status being disarmed, armed-stay and armed-away.