Heavy Duty Switches are intended for use in applicationswhere, Rugged construction, reliable performance, continuity of service and ease of maintenance are emphasized. Available fault currents higher than 10,000A are likely to be encountered, such as in manufacturing plants, massproduction industries and commercial, institutional and other large buildings served by network systems or transformers of higher capacitie. System voltage is 600V AC or DC max and A Type 12 or 4 / 4X enclosure is required. Defeatable dual cover interlocks are standard on all heavy duty switches. Prevents cover from being opened when switch is in the ON position and prevents switch from being turned ON when door is opened.