PLC COMPATIBLE MODELS . CORROSION RESISTANT FINISH . VOLUME ADJUSTABLE . COMPLETELY ASSEMBLED . THE EDWARDS 874 AC SERIES ARE LOW-CURRENT HIGH DECIBEL SURFACE MOUNT VIBRATING HORNS FOR HEAVY-DUTY USE. SUPPLIED COMPLETE WITH ADAPTAPLATE. FOR EASY INSTALLATION. . SUPPLIED ADATAPLATE ALLOWS QUICK PLUG-IN CONNECTION. HORN SIMPLY PLUGS INTO RECEPTACLE ON MOUNTING PLATE. ALSO MOUNTS ON ANY SINGLE GANG 3 1/4″ (83MM) 3 1/2″ (89MM) 4″ (102MM) OCTAGON OR 4″ (102MM) SQUARE BOX. . USED IN INDUSTRIAL COMMERCIAL AND INSTITUTIONAL APPLICATIONS FOR TIMING PAGING AND ALARM SIGNALING. APPLICATIONS INCLUDE EQUIPMENT MALFUNCTION ALERT AND SECURITY WARNING. . 872-PO PLASTIC PROJECTOR ADAPTAHORN ACCESSORY. PLASTIC PROJECTOR SNAPS ONTO ANY ADAPTAHORN. AVAILABLE AS SEPARATE ITEM..