If you call someone, take a look at the front of your phone. You will see a steady red glow from the top left of your screen, this is where the proximity and ambient light sensor are housed.
Do you mean the sensor activated during a phone call? My HTC one X last time has an abnormal behavior when I place a phone call. Normally when you move the phone away of hear it should turn on the screen back light so you are able to hang up the phone call. But my phone still be black after moving away from the hear so I need to push power button to activate the screen back-light and than hang up the phone call. Could somebody help me out on this issue? Any kind of help shall be much appreciated.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?