Contact voltage energizes objects which are normally safe – fences, telephone booths, street signs, etc. Anywhere buried electric wiring exists, a failure can occur in that wiring and create conditions that allow electricity to flow into the immediate surroundings. Some systems have protective devices such as circuit breakers or Ground Fault Circuit Interrupters (GFCI), designed to isolate such a fault. However, in the absence of protective devices, if the devices fail, or if they are not installed correctly, a fault will go undetected until it either causes a failure of the circuit or until it is found by a person.