Numbers stations are shortwave radio stations of uncertain origin that broadcast streams of numbers, letters (using a phonetic alphabet), or words. It is not known publicly with certainty where these signals originate nor what purpose they serve. The voices that can be heard on these stations are often mysterious: mechanically generated; spoken in a wide variety of languages; usually female, but sometimes male or those of children. Numbers stations appear and disappear continuously, although some stick to regular schedules, and their overall activity has increased slightly since the early 1990s.
It has been speculated that these stations operate as a simple and foolproof method for government agencies to communicate with spies "in the field", using the transmitted codes as a one-time pad cryptosystem. As evidence, numbers stations have changed details of their broadcasts or produced "special", non-scheduled broadcasts in response to extraordinary political events, such as the Russian constitutional crisis of 1993. Others speculate that some of these stations may be related to illegal drug smuggling operations. Although no broadcaster or government will acknowledge or give a reason for their existence, a 1998 article in The Daily Telegraph quoted a spokesperson for the Department of Trade and Industry (the government agency that regulates radio broadcasting in the United Kingdom) as saying, "These [numbers stations] are what you suppose they are. People shouldn't be mystified by them. They are not for, shall we say, public consumption."
Numbers stations are often given nicknames by enthusiasts. These nicknames often reflect some distinctive element of the station. For example, "Lincolnshire Poacher", one of the best known numbers stations, supposed by many to be run by MI6, plays the first two bars of the folk song of that name before each string of numbers. "Magnetic Fields" plays music from French electronic musician Jean Michel Jarre before and after each set of numbers. The "Atención" station begins its transmission with the Spanish phrase "ˇAtención! ˇAtención!"
Errors at the transmission site, radio direction-finding, and a knowledge of shortwave radio propagation have also provided clues to number station locations. For example, the "Atención" station is presumed to be from Cuba, as a supposed error allowed Radio Habana Cuba to be carried on the frequency.
On some stations, tones can be heard in the background. It has been suggested that in such cases the voice may be an aid to tuning to the correct frequency, with the coded message being sent by modulating the tones, perhaps using a technology such as burst transmission.
Generally, numbers stations follow a basic format, although there are many differences in details between stations. Transmissions usually begin on the hour or half-hour.
The prelude or introduction of a transmission (which is what stations' informal nicknames are often derived from) includes some kind of identifier, either for the station itself and/or the intended recipient. This can take the form of numeric or phonetic "code names" (ie "Charlie India Oscar", "250 250 250"), characteristic phrases (ie "Atencion! Atencion!", "1234567890"), and sometimes musical or electronic sounds (ie "The Lincolnshire Poacher", "Magnetic Fields"). Sometimes, as in the case of the Israeli phonetic alphabet stations, the prelude can also signify the nature or priority of the message to follow (ie "Charlie India Oscar-2", indicating that no message follows). Often the prelude repeats for a period of time before the body of the message begins.
There is usually an announcement of the number of random-number groups in the message, then the groups are recited. Groups are usually either four or five random digits (or phonetic letters). The groups are usually repeated, either by reading each group twice, or repeating the entire message as a whole.
Some stations send more than one message during a transmission. In this case some or all of the above process is repeated, with different information of course.
Finally, after all the messages have been sent, the station will sign off in some characteristic fashion. Usually it will simply be some form of the word "end" in whatever language the station uses (ie "end of message, end of transmission"; "ende"; "fini"; "final"; "conet"). Some stations, especially those thought to originate from the former Soviet Union, end with a series of zeros, ie "000 000"; others end with music or other sundry sounds.
Recordings and music
In 1997, The Conet Project: Recordings of Shortwave Numbers Stations, a four CD set of recordings of numbers stations was released by England's Irdial-Discs record label.
Recordings of numbers stations sometimes find their way onto records by other musicians, such as Stereolab's song "Pause", Porcupine Tree's "Even Less", Chroma Key's "Even the Waves", or various songs by Wilco. The reclusive Scottish duo Boards of Canada were influenced by numbers stations at an early age. Pere Ubu's Scott Krause is an avid fan of numbers stations and has featured recordings in several songs.
Cameron Crowe also featured parts of the "Conet Project" in scenes of the movie Vanilla Sky. He said he used the station recordings to create a sense of confusion.