Patent ID: 8232878

Claim:
A security system forming a perimeter around an area to be monitored for detecting physical intrusion in the area comprising a plurality of at least three narrow-band, low data rate, low power radio units arranged in a network to form at least one ring around the monitored area, each of said radio units having a signal transmitter, a signal receiver, a circuit coupled with the receiver to measure the signal strength of signals received by the receiver and produce an output representative of received signal strength, a controller responsive to said circuit output to cause said transmitter to transmit a transmitted signal representative of the strength of the signal received by said receiver and to provide said radio unit with a receive mode and a transmit mode such that said receiver and said transmitter do not operate simultaneously, said radio units being positioned such that each radio unit is within communication range of at least one other radio unit and wherein said radio units are arranged such that alternating radio units have an amplifier and the other radio units do not have an amplifier; and a base station positioned to receive said transmitted signal from one of said radio units and to provide an indication of intrusion into the monitored area.