“In iPhones past, the IR proximity sensors would only switch on when a phone or Skype call was initiated. The sensor could detect that a face was near and then smartly dim the display / kill the keyboard, and then resume normal activity once it detected the face was not in close proximity anymore,” iFixit reports.
“The 4S, however, has a neurotic tendency of always wondering how close your face is. As long as the screen is activated, that IR sensor will be shining brightly,” iFixit reports. “So we began to ponder: why is the 4S so interested in our faces’ whereabouts? Well, we believe the answer lies with our new search-servant Siri.”
iFixit reports, “Siri is ready and waiting to answer her master’s beck and call at any time. And in order to be as attentive as a personal assistant ought to be, Apple had to design the proximity sensor to be as vigilant as Big Brother, but as cute as Little Sister. So whenever the screen is active, the proximity sensor is active too. Thus, whenever you raise the iPhone 4S to your face, Siri is ready to take orders.”
Read more in the full article here.