RCDs are often known by other names, earth leakage circuit breakers (ELCB) or safety switches.

An RCD is an electrical safety device specially designed to immediately switch the electricity off when electricity "leaking" to earth is detected at a level harmful to a person using electrical equipment.

An RCD offers a high level of personal protection from electric shock.

Fuses or over current circuit breakers do not offer the same level of personal protection against faults involving current flow to earth.

Circuit breakers and fuses provide equipment and installation protection and operate only in response to an electrical overload or short circuit.

RCDs have another important advantage - they reduce the risk of fire by detecting electrical leakage to earth in electrical wiring and accessories.