Again. Slap yourself. This time you need to repent too. Why? Because you are WRONG. How do you think the original iPhone, 3G, and the 3GS performed the same function (shut the screen off while on a call)???? What could it be? Guesses? Anyone? Bueller?
Proximity sensor! Those previous models never had a front facing camera. The proximity sensor in those models were in the same place the front facing camera is now (4 and 4S). They moved the proximity sensor above the ear speaker. What do you think the strip above the ear speaker is in the white iPhones???????
You can't see it on the black model because it blends in.
Some people.............lol