The Square D by Schneider Electric QO 40 amp One-Pole Circuit Breaker is intended for overload and short-circuit protection of your electrical system. All QO circuit breakers are equipped with the exclusive Visi-Trip indicator. When a QO Visi-Trip circuit breaker trips, the handle snaps to a midpoint position between "OFF" and "ON" and a highly visible, red indicator easily identifies the tripped breaker. This enables you to easily distinguish which breaker has tripped in a load center that may contain up to 42 different circuit breakers. QO circuit breakers have features no other manufacturer can offer.