A residual current device (RCD), or safety switch, protects you from the most frequent cause of electrocution – a shock from electricity passing through the body to the earth. RCDs also protect against fire caused by faults in appliance, tools and wiring. If these faults go unnoticed they could cause a fire or personal injury. RCDs provide a means of early fault detection. RCDs are electrical safety devices designed to immediately switch off the supply of electricity when electricity leaking to earth is detected at harmful levels. They offer high levels of personal protection from electric shock. The majority of electrical workplace injuries and fatalities can be prevented by the use of properly installed, tested and maintained residual current devices. By law most work places have a Residual Current Device (RCD) Testing requirement for electrical equipment under AS/NZS 3760:2010 & AS/NSZ3012:2010 standards. The test for the operating time of a RCD entails specific technical expertise and interpretation of results and, consequently, can only be carried out by an appropriately qualified or trained person. This means a licensed electrician or a person who has successfully completed a competency- assessed training course in the use of a RCD tester.