The A50E-2 is an addressable relay providing single pole, volt free, change-over contacts. The unit is intended for installation within the equipment to be switched, thereby offering savings in installation costs when compared to long, auxiliary circuit, wiring runs out from the control panel. Approved to EN54-18, the relay may be located anywhere on the two core ZP loop and is designed for power up or shut down of building services, for example air conditioning plant, in fire conditions.