Numbers stations are shortwave radio stations of uncertain origin. They generally broadcast artificially generated voices reading streams of numbers, words, letters (sometimes using a spelling alphabet), tunes or Morse code. They are in a wide variety of languages and the voices are usually women's, though sometimes men's or children's voices are used.
Evidence supports popular assumptions that the broadcasts are used to send messages to spies. This usage has not been publicly acknowledged by any government that may operate a numbers station, but in one case, Cuban numbers station espionage has been publicly prosecuted in a United States federal court.
from Simon Mason...
"Here you can access the book "Secret Signals, The Euronumbers Mystery" which was written in 1991 and is now out of print. Thanks to the publisher "Tiare Publications " of Lake Geneva U.S.A. and Gerry Dexter its owner, I am able to reproduce the book..." (more) (audio clip 1) (audio clip 2) (extra credit)
