The Edwards 5570M intercom is a heavy duty UL and cUL listed signal appliance designed for use in industrial and hazardous location applications. The 5570M can be configured by means of a slide switch. The AC line has a 1/2 A 250 V type GMC fuse. Operating selections include balanced or unbalanced line operation and modes of Master or Satellite can be selected. The unit features a transformer isolated audio input and a choice of one of four selectable alert tones. For indoor applications where ambient noise is high, a hand-held noise cancelling microphone kit is available.