888D and 74339U hazardous location horns are diode-polarized, heavy duty, high decibel vibrating horns intended for use in life safety systems in hazardous (classified) and outdoor locations. These horns may be mounted to any solid surface using two bolts (by others). Each unit is supplied with a sealing fitting for ¾-inch -14 National Pipe Taper (NPT) nipple, and wire leads for the electrical connection to the life safety system notification appliance circuit.