Square D 8501-HO-40 AC control relay, 110–120 V AC coil, Series D. This is a NEMA-style control relay in Square D’s Class 8501 family used to switch a separate AC load in control circuits, panels, and machine tools when the coil is energized. The HO-40 designation identifies the specific variant within the 8501 line, providing the compact, cartridge-style form factor typical of 8501 relays for reliable industrial control applications.
