Radio

Radio is the use of electromagnetic waves for communication. This is used both for broadcast (one-to-many) and point-to-point (one-to-one) communication of voice, music, code, and other data. Transmission of video by radio waves is known as television. Transmissions can be analog or digital. These days, broadcasts are often simulcast on the Internet as well.

Transmission modes

 * AM
 * FM

Digital data and metadata

 * Broadcast Metadata Exchange Format
 * Radio Data System (RDS, RBDS)

Emergency broadcasts

 * CONELRAD
 * Emergency Alert System (USA current)
 * Emergency Broadcast System (USA old)
 * AlertReady (Canada)

Other

 * Call sign (call letters of stations)

See also Audio and Music and Video for particular encoding formats for those types of media, and Morse code (which is under Character Encodings).