This document provides an overview of infrared sensors. It discusses that infrared sensors can detect infrared radiation emitted or reflected by objects and are used to sense characteristics of the surrounding environment. The key elements of an infrared detection system are an infrared transmitter, transmission medium, and infrared receiver. Common applications of infrared sensors include proximity sensors, item counters, burglar alarms, and human body detection. The advantages are low power requirements and simple circuitry, while the disadvantages include a line of sight requirement and short range.