The UR15-42 is a trip-free DC high-speed current limiting air circuit-breaker, single pole unit, bi-directional, with electromagnetic blowout, direct instantaneous over-current release, natural air-cooling and electrical operating system. The UR15-42 is mainly used to protect propulsion and auxiliary equipments mounted on rolling stock and can also be delivered enclosed in a special protective box for vehicle underframe mounting. The UR15-42 is also used as line breaker for light duty DC traction substation as well as for various industrial applications.