Patent ID: 7129842

Claim:
A MEMS (micro-electronic mechanical system) sensor unit, for a security system having an RF receiver, that provides both an immediate alarm signal upon detection of motion as well as an out of range condition, comprising: a battery power supply, a MEMS sensor, a short range RF transmitter, and a controller to control operation of the MEMS sensor unit; wherein initially the MEMS sensor unit is in a power conservation, normal supervision mode in which the MEMS sensor unit transmits a normal status RF signal to the security system receiver on an infrequent normal supervision interval; upon sensing motion, the MEMS sensor unit transmits a motion signal to the security system receiver indicating that the MEMS sensor unit has been moved, and then sends supervision signals to the security system receiver on a more frequent interval than the normal supervision interval; after the MEMS sensor unit senses that it has returned to a stationary state, the MEMS sensor unit transmits a stationary signal to the security system receiver indicating the return to a stationary state, and the MEMS sensor unit then returns to the normal supervision mode, transmitting a normal status signal on an infrequent normal supervision interval; if the MEMS sensor unit is moved out of range of the security system receiver before the stationary message is received by the security system receiver, as indicated by the security system receiver not receiving one or more of the frequent supervision signals, the security system indicates an alarm condition.