The Alpha Communications/TekTone PK152 annunciator control unit is used to provide power and control circuits to operate the NC110N, NC150N, NC150R and NC200N series nurse-call and area of refuge (area of rescue) type systems and annunciators. The PK152 contains the electronic circuitry necessary to detect the presence of routine and emergency calls, and to generate audible and visual control signals. It provides steady or intermittent voltages to operate visual signaling devices. The PK152 supports up to 1A of current load from the field devices, and supports interconnection of a secondary power supply (PK800A) to increase the output current load to 3A. Protective circuitry has been incorporated to protect routine and emergency call commons from shorts. Each master station requires it's own PK152 for power and control.