Square D QO Circuit Breaker QO circuit breaker for use in QO load centers. Intended for overload and short-circuit protection of electrical systems. ANSI American National Standards Institute certified and UL Underwriter's Laboratories listed. Rated for 120 volt/240 volt and 10,000 AIR. Features the exclusive Visi-Trip indicator. When the circuit breaker trips, the handle snaps to a midpoint and a highly visible red indicator easily identifies the tripped breaker. QO circuit breaker for use in QO load centers. Intended for overload and short-circuit protection of electrical systems. ANSI American National Standards Institute certified and UL Underwriter's Laboratories listed. Rated for 120 volt/240 volt and 10,000 AIR. Features the exclusive Visi-Trip indicator. When the circuit breaker trips, the handle snaps to a midpoint and a highly visible red indicator easily identifies the tripped breaker.