I needed a new fuse box fitted but some additional faults were found before the job could be completed.
RCD stands for Residual Current Device. An RCD is a safety device within a fuse board that switches off electricity automatically if there is a fault detected. It will continuously monitor the electric current flowing along a circuit. If there is an earth fault, the RCD will sense a leakage and trip disconnecting the supply of electricity minimising the chance of fatal electric shock.
RCDs are an essential safety device and every home should have one.