A type of circuit breaker designed to protect equipment from continued electrical current in case of a circuit fault. The current in the hot wire and the neutral wire of an AC circuit are normally the same. However, if a fault in the circuit allows some of the current to leak to a ground, there will be a difference between them. The GFI monitors the current flow and opens the circuit if it detects a difference of more than 4 to 6 milliamps. This sensing and interruption takes place in less than 1/10th of a second, preventing damage to electrical equipment.