The masterplug mstarcdkgmp rcd safety adaptor plug simply plugs into the mains then you plug your electrical appliance into it if there is a fault or a short in the tool you are using the unit cuts the power very quickly reducing the risk of electrocution the masterplug safety rcd adapter continuously monitors the power supply to an electrical appliance and cuts off the power within 40 milliseconds if an earth current fault is detected this is fast enough to prevent a fatal electric shock the ma