Edwards Signaling 878DEX-N5 Horn, Fire Alarm, Hazardous Location, 120V AC, Gray. Diode polarized, heavy-duty, high decibel, vibrating horn signals are what the Edwards 878DEX, 879DEX, 888D, and 889D series of signals are. They are designed for usage in risky environments where the electrical surveillance of signaling circuit field wiring is necessary. The 878DEX and 879DEX have a NEMA type 4X classification, are suitable for non-fire alarm applications, and can be used outdoors (recommended above +25F temps). For wall mounting, there are two mounting brackets available on either side of the unit. To enable field wire installation, the housing is tapped for 3/4" (19mm) conduit on one side. For usage in dangerous, dusty environments when a recognizable, urgent alert is needed. Use in mines, petroleum refineries, gas refineries, grain elevators, wheat mills, paper mills, textile factories, and tankers are just a few examples of typical applications.