Radios are communication systems that send and/or receive electromagnetic waves. Devices such as citizens’ band (CB) radios, walkie-talkies, and handie-talkies are two-way radios that can be used for interpersonal communications. Two-way radios consist of a transmitter, receiver, and antenna. They are available in mobile and base configurations. Unlike cellular phones, radios do not require a monthly contract or carry per-call charges. In the United States, two-way radios are regulated by the Federal Communications Commission (FCC) and use ultra high frequency (UHF) and very high frequency (VHF) bands. UHF radios use line-of-sight communications and repeaters. They provide better reception than CB radios, which can use either HF 27 MHz or UHF 477 MHz. VHF radios are used mainly in marine applications and by emergency personnel. VHF/UHF two-way radios are also available. Radio accessories include two-way antennas, UHF connectors, battery chargers, and external GPS receivers.