Siri on iPhone 4S comes up with many power features to enrich the user experience on the device, along with many powerful search engine features carries the “Raise To Speak” feature on iPhone 4S that allows Siri to launch on a device whenever “Raise To Speak” activated iPhone 4S raise to the user’s ear. The raise to speak feature uses the couple of iPhone 4S features, such as the proximity sensors to sense the raising action of the device and to sense how close the user’s face is to the screen. Apple has already powered their iPhone with proximity sensors to sense the closeness of a screen to the user’s skin in order to turn off the device display and touch to prevent accidental input while on phone calls.

However,it appears the new Siri “Raise To Speak” feature requires the proximity sensors to work all the time and silently allow them to eat all the battery of the device. Similar to “Setting Time Zone” bug of iOS 5. In addition to it, the infamous Teardown specialist firm named “iFixit” comes up with a report showing how the new iPhone 4S proximity sensors involved in emitting infrared lights to detect the user’s skin for Siri’s new Raise To Speak feature.

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.

iFixit folks have demoed a video showing comparison between the iPhone 4 and iPhone 4S proximity sensors wwork. Thefirm highlights how iPhone 4 sensor activate when the user on pa phone call,and how the iPhone 4S new proximity work all the time to support the new iPhone 4S Siri’s “Raise to Speak” feature.