Antennas are electromagnetic devices designed to send and receive radio waves. They are used in radio and television broadcasting, cellular communication, wireless networking, two-way radio communication, satellite communications and other forms of radio communication. Antennas come in many shapes and sizes, each designed for a specific purpose. Broadcasts antennas typically consist of multiple thin wires suspended in air, while antennas used in mobile devices can be as small as a few millimeters. Antennas convert energy between electromagnetic (radio) waves and electrical signals, allowing for long-distance communication. The size of an antenna and the frequency of the signals it transmits and receives determines the type of antenna that needs to be used.