An electric contactor is a large relay for switching electrical loads on and off in motors and other high-power loads. IEC magnetic contactors provide precise ratings for power-circuit switching and automatic cutoffs during power failures. NEMA magnetic contactors are commonly used as motor contactors and for switching heating loads, capacitors, and transformers in construction, infrastructure, oil and gas, and industrial automation applications. Definite-purpose magnetic contactors control electric loads in HVAC, data processing, and food-service applications. Lighting contactors are used on lighting circuits. Hoist contactors control electric hoists, light-duty cranes, and door operators. Mercury displacement contactors use mercury as contact material to open and close circuits in electric transformers, capacitors and heaters.