An RCD (residual current device) is a safety device that is designed to protect against electrical shocks and fires by detecting imbalances in the electrical current and shutting off the power in the event of a problem. RCDs are commonly used in homes and other buildings to provide an additional level of protection against electrical accidents and are typically installed in the electrical panel or at the point of use. They are an important safety feature that can help to prevent serious injuries or damage to your home in the event of an electrical malfunction or problem.