OF Auxiliary Switch Linked to the left side of NDM1 series MCB Indicate the OPEN or CLOSED status of the associated breaker SD Alarm Switch Linked to the left side of NDM1 series MCB Indicate the tripping status of the associated breaker MX+OF Shunt Release Linked to the right side of NDM1 series MCB Remote control NDM1L Residual Current Unit Installed on the right side of series NDM1 MCB Protection against earth leakage faults NDH1 Busbar & NDH2 Busbar Linked to NDM1-63 series MCB line terminals of the same phase