Revision Standard - Active. Metal-enclosed, low-voltage switchgear—which contains either stationary or drawout, manually or electrically operated low-voltage ac or dc power circuit breakers in individual metal compartments, in three-pole, four-pole, two-pole, or single-pole construction—is covered. Rated maximum voltage levels are 254 V, 508 V, 635 V, 730 V, or 1058 Vac; and 300/325 V, 600 V, 800 V, 1000 V, 1200 V, 1500 V, 1600 V, or 3200 Vdc. The preferred continuous current ratings of the main bus in ac designs are 1600 A, 2000 A, 3000 A, 3200 A, 4000 A, 5000 A, 6000 A, 8000 A, or 10 000 A. For dc designs, the preferred ratings are 1600 A, 2000 A, 2500 A, 3000 A, 4000 A, 5000 A, 6000 A, 8000 A, 10 000 A, or 12 000 A. The switchgear may also contain associated control, instruments, metering, protective, and regulating devices as necessary. The standard deals with service conditions, ratings, temperature limitations, and classification of insulating materials, insulation (dielectric) withstand voltage requirements, test procedures, and application.