​Applies to a.c. circuit-breakers designed for indoor and outdoor installation and for operation at frequencies up to and including 60 Hz on systems having boltages above 1000 V, and to the operating devices of circuit-breakers and to their auxiliary equipment, It applies only to three-pole circuit-breakers for use in three-phase systems and single-pole circuit-breakers for use in single-phase systems. Two pole circuit-breakers for use in single-phase systems are subject to agreement between purchaser and manufacturer.