A controller for use in a security system based upon RFID techniques. The controller can use power line carrier communications to communicate with other devices in the security system. The controller can use a modem or wireless module to connect to public networks. Multiple controllers can be used in a system, and the controllers can arbitrate to determine a master controller. The controller contains configuration data and tables that define the relationships between devices in the security system. The controller can receive communications from other devices in the system and can interface with legacy devices previously used with wired security systems. The controller can send messages based upon predetermined events, and can support a remote alerting function.