GFS and GFSX ground fault circuit interrupters are used in Class I and Class II hazardous locations with portable electrical equipment such as tools, lighting systems, compressors and similar devices for personnel protection.GFS/GFSX GFCIs are used in branch circuits of 15 to 20 amperes at 125 volts AC in conjunction with Crouse-Hinds series ENR/ENRX or CPS receptacles.