How does the iPhone know when you pull the phone away from your face?

[OrlandoTragic]

You know how the screen goes black when you're on a call unless you pull the phone away from your ear, at which point, it lights up??

Is it sensing heat from your ear, or noise (or lack thereof) coming from the mic?

 

[Zwhaler]

There is a proximity sensor next to the earpiece. While on a call you can activate it by using your finger if you wanted, in other words it doesn't use the mic to detect when your face is there.

 

[Rhosfelt]

There is a proximity sensor next to the earpiece. While on a call you can activate it by using your finger if you wanted, in other words it doesn't use the mic to detect when your face is there.

In other words, magic.

 

[neesh0]

make sure you dont use a case that blocks the sensors, if you do you are gonna have a hard time hanging up!

 

[rsk137]

There are 3 sensors right to the left of the earpiece and one of them controls the function of locking your screen. You can't see them unless you hold the phone under direct light.

It locks once the sensor is covered or obstructed.