An RCD, or residual current device, is an electrical safety device that is designed to prevent electric shocks or electrocution by quickly breaking an electrical circuit with leakage current to ground. It constantly monitors the electric current flowing through one or more circuits it is used to protect. If it detects electricity flowing down an unintended path, such as through a person who has touched a live part, the RCD will switch the circuit off very quickly, significantly reducing the risk of death or serious injury. RCDs are testable and resettable devices, and they come in different types based on the place of installation, such as fixed/mains type, outlet type, and portable type. Some RCDs disconnect both the energized and return conductors upon a fault (double pole), while a single pole RCD only disconnects the energized conductor. RCDs are designed to protect against the risks of electrocution and fire caused by earth faults.