HTC One M8 User Manual page 48

48 Your first week with your new phone
Flip to mute
If your phone is facing up when a call
comes in, turn the phone over to mute
it.
If you go to Settings and then tap
Sound > Flip to mute, you can set your
phone to:
Mute Mute only once after
once flipping the phone. While
the phone is still facing
down, it will ring again when
there are other incoming
calls.
Mute After flipping the phone to
always mute a call, keep it always
muted while it's still facing
down when there are other
incoming calls.