How do I use the controls on the H820e?

The volume up/down and mute buttons are located on the microphone side of the headset.
Here's how to work the volume controls:

To turn the volume up, press the button with raised dots — you'll hear a high-pitched tone while the volume increases.
To turn the volume down, press the button with recessed dots — you'll hear a lower-pitched tone while the volume decreases.
Press the button on the boom to mute the microphone.

To answer or end a call, use the controls on your softphone or in your conferencing application.

Logitech Business Support