Square D 8903-SV012 is a lighting contactor used in commercial and industrial electrical systems to control large lighting or power loads. It has multiple poles (typically three) and is actuated by a control coil (often 120 V AC) that closes the main contacts when energized. The contactor is designed for frequent switching and can handle substantial current safely, making it suitable for lighting circuits, fan loads, or other commercial equipment. It is typically mounted in panelboards, control cabinets, or lighting control centers. Square D 8903 series contactors are valued for durability and long service life in demanding electrical applications.