The new iPhone 4S function namely Siri personal assistant includes a “raise to speak” feature through which Siri is activated every time an active iPhone is raised to the ear of the user. This is done with the help of a proximity sensor that detects how close the screen is to the user’s face.
Proximity sensors have always been part of iPhone as they prevent accidental input during phone calls by turning off the device’s display. However, Siri raise to speak feature is different in a way that it keeps the device ready every moment to sense proximity to the user’s face.
Teardown firm iFixit has analyzed iPhone 4S to shed light on the sensor involved and identify how it emits infrared light to hold up Siri’s raise to speak function at all times.
“During our iPhone 4S teardown, iFixit buddy Markus noted that the new iPhone had a rather unusual-looking black component next to the ambient light sensor. We didn’t make much of a fuss about it since we were knee-deep in disassembly pictures, but the little black box certainly piqued our curiosity. Now that the teardown is wrapped up, we’ve re-opened the mystery and made a neat discovery about the 4S: that black component is an infrared LED, and the little bugger almost always wants to know if you’re nearby.”