What Can I Do During A Call - HTC One User Manual

Place HTC One face down on a level surface.
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If HTC One is already facing down, it will still ring when there are
subsequent incoming calls.
Look who's calling
Every time you make a call or your friend gives you a ring, you get to see
your friend's latest social network status update right on the call screen.
You'll also see a birthday reminder if your friend's birthday (stored on your
phone or online account) will happen in a few days.
Viewing a task reminder while on a call
Did you promise to babysit for a friend this weekend? If you associate a
task with a due date to a contact, you'll see a task reminder on the call
screen when you're on a call with that friend.
If the contact has a recent status update, you won't be able to see
the task reminder.

What can I do during a call

When a call is in progress, use the buttons onscreen to mute or unmute the
microphone or to turn the speakerphone on or off.
Phone calls 109