Abstract: A plurality of remotely located transponder units each communicate with a central station unit to provide a full array of alarm and status signals to the central station. The transponder units are capable of remotely addressing the central station unit directly, without the need for human intervention at the central station, to alter subscriber opening and closing times, passwords, and other system parameters. The transponder also permits defective zones to be shunted either from the central station or locally pending repair, testing and status checks.