An RFID reader for use in a security system based upon RFID techniques. The RFID reader can use power line carrier communications to communicate with the controllers in the security system. The RFID reader of the security system can be provided with multiple modulation techniques, multiple antennas, and the capability to vary its power level and carrier frequency. The controller of the security system determines which RFID readers may transmit, at what times, and the parameters with which to transmit. The RFID reader can detect interference or jamming, and respond. The RFID reader can transmit RF energy useful for detecting motion or for charging the batteries in RFID transponders. The RFID reader can receive wireless communications from active transmitters or from other RFID readers.