Numbers stations are shortwave radio stations of uncertain origin. They generally broadcast artificially generated voices reading streams of numbers, words, letters, tunes or Morse code. They are in a wide variety of languages and the voices are usually female, though sometimes male or children’s voices are used.
It has been reported that the United States uses numbers stations to communicate encoded information to persons in other countries. Others speculate that some of these stations may be related to illegal drug smuggling operations.
According to the notes of The Conet Project, numbers stations have been reported since World War I. They appear and disappear over time, although some follow regular schedules, and their overall activity has increased slightly since the early 1990s. This increase suggests that, as spy-related phenomena, they were not unique to the Cold War.
Numbers stations are often given nicknames by enthusiasts, often reflecting some distinctive element of the station such as their interval signal. For example, the “Lincolnshire Poacher” played the first two bars of the folk song “The Lincolnshire Poacher” before each string of numbers. “Magnetic Fields” plays music from French electronic musician Jean Michel Jarre before and after each set of numbers.