What Are Numbers Stations?

Although no one knows for sure. Numbers stations are thought to be coded broadcasts, or instructions, from intelligence agencies to undercover field agents deployed abroad. The advantage to this method of communication is that the agent in question requires nothing more than a shortwave radio to receive the message.

Articles on Numbers Stations:

Secret Signals - The Euronumbers Mystery
Numbers Stations on Shortwave Radio
The Mystery of the Numbers Stations
Shortwave Spy Numbers Stations
Random numbers on shortwave add up to one thing: Spies!
Number Nine, Number Nine...

Sound Files:

File 1: German Bravo Lima
File 2: German Charlie Delta
File 3: German Counting Station
File 4: German "Strich" Message
File 5: American Nato Alphabet Station
File 6: MOSSAD Nato Alphabet Station
File 7: MOSSAD Alphabet Station
File 8: Spanish Counting Station