A proximity sensor is a standard feature of most smartphones, including Android and Samsung devices. It is a small hardware component that detects the presence of nearby objects without any physical contact. The proximity sensor consists of a light-emitting and light-receiving component, and it emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance) and looks for changes in the field or return signal. The primary function of the proximity sensor is to conserve battery life and prevent accidental inputs. When you make or receive a phone call, for example, the proximity sensor detects when you hold the phone to your ear and automatically turns off the screen. This feature eliminates accidental touch inputs during the call and also saves battery power.

The proximity sensor is typically placed next to the speaker area at the top of the phone. It detects human skin within a certain distance and is most commonly used to detect when the phone is held to the face. The phone uses this information to temporarily power down the display and the touch screen, to prevent the face from accidentally touching on-screen buttons and triggering unwanted actions. There are multiple types of proximity sensors, employing different technology. One type projects an invisible beam of infrared light and measures the beams reflection from nearby surfaces. Another type uses capacitive technology (like touch-screens) that uses an electric field to detect the unique electrical properties of human skin.

In summary, a proximity sensor is a small hardware component that detects the presence of nearby objects without any physical contact. It is most commonly used in smartphones to detect when the phone is held to the face and to conserve battery life and prevent accidental inputs.