Posted to rec.radio.shortwave:
Richard Syrett on CFRB 1010:
Richard spoke with a shortwave radio enthusiast and author/researcher about Spy Number Stations. Numbers stations are shortwave radio stations of uncertain origin. They generally broadcast voices reading streams of numbers, words, letters (sometimes using a radio alphabet), tunes or Morse code. Evidence supports popular assumptions that the broadcasts are channels of communication used to send messages to spies.
http://www.swldxer.co.uk/cfrb.wma--
Simon Mason
http://www.simonmason.karoo.net/