Numbers stations are radio stations that utilize shortwave signals to transmit broadcasts that consist primarily of a voice stating a series of numbers without other instruction or indication of purpose. These various stations have been broadcasting for decades, with reports dating back to just after the Second World War. The numbers spoken are typically repeated several times and listed in groups of either four or five digits together. This has led many researchers to suspect the stations are used to transmit secret codes and messages. Numbers stations have been heard in different languages, including English, German, and Spanish, and while no country has openly declared using them, they are thought to be used in sending messages to spies.
The first numbers stations were discovered by radio hobbyists who were scanning various frequencies looking for similar hobbyists broadcasting messages. These stations were first identified following World War II and seemed to utilize similar technology and methods to those used during the war to transmit messages and weather reports between positions. Though various numbers stations have been identified and are discussed using nicknames by researchers, numbers stations tend to broadcast on several different frequencies at different times. There will often be a set schedule for these broadcasts, however, and similar methods used on different frequencies are often the sign of a single station.
A broadcast on a particular numbers station will usually last only a few minutes, and it often begins with a short indicator that the broadcast is about to begin. One station, which is believed to have been British in origin, uses a brief excerpt from the English song The Lincolnshire Poacher, leading to this name being used to refer to the station. This is then followed by a voice reading off groups of numbers. This voice is often female and based on the way in which the numbers are read it seems to be a mechanized or computer generated voice. Each group of numbers is typically given several times, followed by a signal afterward to indicate the end of the broadcast.
Since no country has yet officially admitted to using numbers stations, there is still no official explanation for any of these stations. It is believed that numbers stations are used to transmit signals to spies, who have been given a cipher key to translate the numbers into a message. Since these messages have not yet been deciphered by researchers, it is believed that “one time pads” are used, which are ciphers used only a single time and are therefore virtually impossible to decipher. Whether numbers stations are used to send actual messages to spies, or merely to create the impression of covert activity in a particular area, however, is still unknown.