XBOX ONE - Hearing Safety and Warranty Information; Hearing Safety Guidelines; Medical Device Precautions; Limited Warranty Overview

Battery compartment cover (15): Sits on the middle back of the controller.
3.5-mm port (16): This is a recessed port next to the expansion port on the bottom-side edge of
the controller. Used to connect compatible 3.5-mm audio devices. Only available on controllers
released after June 2015.