The Siemens 3RT5975-5AF31 is a SIRIUS magnet coil for size S12 contactors. The coil accepts both AC and DC control supply voltage at a rated value of 127 V for 50 Hz, 60 Hz, and DC operation. That 127 V DC rating is worth flagging: if your control bus is 125 VDC nominal, this coil holds right at its rated value — no margin concern. The AC/DC capability simplifies stocking; one coil covers both supply types at the same voltage level.
Integration note — panel fit
The coil mounts directly into the S12 contactor frame. Verify the control voltage before energizing — 127 V AC/DC.