The Square D by Schneider Electric brand Heavy Duty Safety Switch is designed to be tough, reliable and provide exceptional performance in the most grueling conditions. Electrical interlocks for Series F, 60A, fusible, general duty safety switches, are available in kit form for field installation. Each kit contains instructions for proper field mounting. A pivot arm operates from switch mechanism, breaking the control circuit before the main switch blades break. Switches with electrical interlocks installed are UL Listed. For factory-installed electrical interlocks add EI (for one contact) or EI2 (for two contacts) suffix to catalog number.