# Bluetooth ## What is Bluetooth Bluetooth is a short-range wireless technology standard used for exchanging data between fixed and mobile devices over short distances. It was developed as a cable replacement technology to connect devices like headsets, keyboards, mice, and printers to computers and smartphones without wires. Bluetooth uses radio waves in the 2.4 gigahertz frequency band, the same band as WiFi, and uses frequency hopping spread spectrum to reduce interference. The Bluetooth Special Interest Group oversees the development and licensing of Bluetooth technology. ## Bluetooth Versions and Speed Bluetooth 1.0 achieved data rates of about 1 megabit per second. Bluetooth 2.0 with EDR, Enhanced Data Rate, increased speeds to 3 megabits per second. Bluetooth 3.0 added high-speed mode using 802.11 WiFi for data transfer, with Bluetooth handling connection setup. Bluetooth 4.0 introduced Bluetooth Low Energy, designed for devices that require very low power consumption such as fitness trackers, heart rate monitors, and other IoT sensors. Bluetooth 5.0 quadrupled the range and doubled the speed of Low Energy mode. The range of standard Bluetooth devices is typically 10 meters for most consumer devices, though class 1 devices can reach 100 meters. ## Bluetooth Profiles Bluetooth defines a set of profiles that specify how Bluetooth should be used for different types of applications. The Advanced Audio Distribution Profile is used for wireless audio streaming to speakers and headphones. The Hands-Free Profile is used for wireless connections between phones and car audio systems. The Human Interface Device Profile is used for keyboards, mice, and game controllers. The File Transfer Profile allows file exchange between devices. The Serial Port Profile emulates a serial cable connection. Devices must implement the appropriate profiles to interoperate for a specific function. ## Bluetooth Pairing Before two Bluetooth devices can communicate, they must be paired. Pairing establishes a trusted relationship between devices and may involve entering a PIN or passphrase. Once paired, devices can automatically connect to each other when within range without repeating the pairing process. Different Bluetooth versions use different pairing methods to improve security.