Kensington H3000 Bluetooth Over-Ear Headset - Manual (Page 6)

6. Use your earcup controls to maximize your productivity. Locate the volume buttons on the side of the earcup. Press the "+" button to increase the volume and the "-" button to decrease the volume.
The center button on your earcup has many functions. Press the center button once to play or pause music. Press the center button three times to turn sidetone on or off.