Often called Breaker for short. A device used in electrical circuits that protects them from overload, like a fuse. A circuit breaker is a switch that will open when the current flow in a circuit goes beyond its rating. Unlike a fuse, however, circuit breakers can be reset. Breakers are generally rated in amps, where the rating specifies the maximum current that can pass before it will open the circuit. The circuit opening (or breaking) may be triggered by heat, magnetic fields, or other side effects of current flow, depending on the design of the breaker.