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riggerman0421
Well-Known Member
It turns the screen off when talking on the phone. This prevents you from pushing any on screen buttons with your cheek. If you'd like to test it, make a call, then ,while it's ringing, cover the top black portion of your screen to the left of the HTC logo. You should see your screen turn off.
benslgdroid
rockstar
I believe it is also what is used for the auto brightness and the key backlights