Patent ID: 7538680

Claim:
An alarm system comprising: a base communication device configured to communicate wireless signals within a range of frequencies; a remote communication device configured to communicate with the base communication device using the wireless signals, wherein the remote communication device is adapted to be associated with an article to be secured and wherein the remote communication device comprises alarm circuitry; wherein the remote communication device comprises an antenna circuit configured to receive the wireless signals communicated by the base communication device and to generate first electrical signals corresponding to respective ones of the received wireless signals, and the remote communication device further comprises a detector comprising a non-linear device configured to receive the first electrical signals and to provide second electrical signals having a non-linear relationship to the first electrical signals, wherein the detector further comprises a parallel LC circuit configured to provide increased impedance at the range of frequencies of the wireless signals compared with other frequencies outside of the range of frequencies; and wherein the remote communication device further comprises processing circuitry coupled with the non-linear device and configured to process the second electrical signals and to control the alarm circuitry to generate a human perceptible alarm responsive to the processing.