Applies to fuses incorporating enclosed fuse-links with rated breaking capacities not less than 2 kA, intended for protection of power frequency a.c. circuits, and also to fuse-links intended for use in fuses combined with mechanical switching devices but does not apply to the device nor does it apply to miniature fuses. Definitions, standard conditions for operation in service, classification, characteristics of fuses, markings, conditions for construction, and tests are covered.