Coil voltage and what it drives
The S-N21-COILAC120V is the replacement coil for Mitsubishi Electric's S-N21 series contactors, wound for 120 VAC control voltage. That 120 VAC rating means it pulls in the contactor when the control transformer or PLC output delivers 120 VAC across the coil terminals — standard for North American panel control circuits running off a 120 V control transformer.