HTC Desire 820 User Manual page 23

23 Your first week with your new phone
If you go to Settings and then tap Sound > Flip to mute, you can set your phone to:
Mute once Mute only once after flipping the phone. While the phone is still facing
down, it will ring again when there are other incoming calls.
Mute always After flipping the phone to mute a call, keep it always muted while it's
still facing down when there are other incoming calls.
Pick up to lower volume
In a business meeting or restaurant, pick HTC Desire 820 up when a call comes in to
lower the ring volume automatically.
You can turn this feature on or off. Go to Settings, tap Sound, and then select or clear
Quiet ring on pickup.
Increase ring volume automatically while phone is in your pocket or
bag