Let's suppose you're talking to someone and need to use keypad.
You take the phone, it turns on the screen, you press something, then you're continuing listening it via the loud speaker.
Then at one moment android dims the screen and then finally turns it off.
Now you're stuck - you cannot press the power (not sure how to call that button) because it would terminate the call. And the screen is not responsive since it turned off.
So how do you deal with it?