This is an insulation monitoring module for 4 poles Compact NSX 100/160/250 that detects and indicates an insulation drop.A Led goes on and an auxiliary contact switches when insulation drops below a minimum.The rated voltage is between 200VAC and 440VAC 50/60Hz.It is installed directly on the device terminals.This insulation monitoring module is self-powered internally by the distribution system voltage, even is supplied by only 2 phases.There is a class II insulation level between the front face and the power circuits. This protection degree is IP40.