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.