A device that provides protection against electrocution by turning off the power when it detects dangerous currents flowing between a phase wire and the ground. Since very small currents passing through a person can cause death, the GFI is designed to sense ground fault currents far below the trip levels of a circuit breaker, and to remove the power in a very short time. A typical GFI will detect and operate on current levels of a few millionths of an ampere and will remove power in less than a thousandth of a second. (see: Ampere; Current; Ground; Circuit Breaker)