The RCM420-D-2 is a residual current MONITOR, and the distinction from a residual current relay is the point of it: it does not trip the circuit, it measures the residual current continuously and reports it. That is what suits it to installations where an unplanned disconnection is more dangerous or more expensive than the fault itself — process plant, shipboard and offshore systems, medical locations, IT networks — where the requirement is to know that insulation is degrading and to schedule the repair, not to drop the load. It is a type A device, responding to sinusoidal AC and pulsating DC residual currents. The supply is a wide-range AC/DC 70-300 V at 42-460 Hz, and measurement is taken through an external summation current transformer of the type W range, which is ordered separately and sized to the cable it encircles. Connection is by screw terminals. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.