Siri-Enabled Proximity Sensor in iPhone 4S

During a detailed disassembly by iFixit of the iPhone 4S, a mysterious component was uncovered. Further investigation revealed that this component is an infrared LED, which serves as an additional proximity sensor linked to Siri’s functionality.

Previous iPhone models included a proximity sensor that turned off the touchscreen when the phone was held close to the face during calls, preventing accidental touch inputs.

This sensor was typically active only during calls or while using VoIP applications such as Skype.

However, the newly discovered infrared LED differs as it remains active continuously when the “Raise to Speak” feature is enabled in Siri’s settings. Its primary role is to activate Siri when the phone is lifted to the ear, rather than deactivating the touchscreen.

Even though the LED is always on when “Raise to Speak” is activated, it consumes very little power, which likely does not contribute significantly to the reported battery problems of the iPhone 4S.

These issues are expected to be addressed in a future update to iOS 5. iFixit notes humorously that despite the constant infrared emission, the beam is entirely harmless to users.


Matthew is a dedicated writer for TUAW, bringing insightful and engaging content to Apple enthusiasts around the world. With a deep love for all things Apple, Matthew covers everything from the latest iPhone and iPad releases to MacBook innovations and Apple Watch updates. His articles are known for their clarity and depth, making complex tech topics accessible to everyone. When he’s not writing, Matthew enjoys exploring new apps and testing out the latest Apple gadgets.