30904 – An RCD, or residual current device, is a life-saving device which is designed to prevent you from getting a fatal electric shock if you touch something live, such as a bare wire. It can also provide some protection against electrical fires. RCDs offer a level of personal protection that ordinary fuses and circuit-breakers cannot provide. Air circuit breakers (ACB) can be used as the main circuit breakers of power distribution systems for buildings, factories, ships, and more to realize high-level circuit monitoring and friendly networking.