The ABB 2CSM242120R1201 is an RD2 residual current monitor (RCM). Unlike an RCD, it does not break the circuit itself: it measures the leakage current flowing through an external toroidal transformer and signals through its output contact, so the tripping is done by a separate breaker or contactor — or not at all, where the requirement is to warn about deteriorating insulation while keeping a process running. Sensitivity and intervention time are set with the minidip switches on the front. This makes it the usual choice for monitoring large or continuous-process installations, and for retrofitting earth-fault monitoring where the existing breaker cannot be changed. It is a Type A device, so it detects sinusoidal AC and pulsating DC residual currents. Sensitivity and tripping delay are both set on the device, which is what lets one part number cover a range of installations and lets discrimination be arranged with the devices downstream. Supply voltage is 48 … 150 V AC/DC. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.