A circuit breaker is a switch designed to protect your device from damage caused by electrical overload or short circuit. When it detects a fault condition, it switches off and interrupts the flow of electricity. The function of a circuit breaker is similar to that of a fuse, except a circuit breaker doesn't need to be replaced every time it goes off, just reset. AC Circuit breakers are breakers specifically for devices that use AC (Alternating Current) power. DC Circuit Breakers are designed to handle DC (Direct Current) power. AC power is what we use every day.