Square D 8903SP011 is a lighting contactor designed for commercial and industrial electrical systems. It is a multi‑pole switching device that uses an electrically energized coil to open and close its main contacts, allowing it to control large lighting loads or other power circuits remotely. When the control coil (often 120 V AC) is energized, the contactor closes the load contacts to supply power; when the coil is de‑energized, the contacts open to interrupt the circuit. These contactors are built for frequent cycling and long‑term reliability in panelboards, motor control centers, and lighting control applications. They are widely used in buildings, factories, and other installations where remote load switching is required.