Numbers STations

Now recently while surfing around the web, I bumped into something very interesting yet creepy. All around the world there are radio stations called Numbers Stations (NS) that broadcast certain signals or sound at different intervals throughout the day. What are these sounds? They are beeps and tones, sometimes even voices repeating a set of tones. Why are they broadcasting this? These numbers stations are supposedly used by spies to overlay messages between each other. Now the reason for this theory comes from the Cold War. Supposed NS sprang up all over the world during the Cold War and some messages were intercepted and decode. The information contained were classified military talk are plans. A lot were used during the Vietnam war and some broadcast were used to plan out NVA troop movements above ground and underground in their rat holes. Most NS also relay messages to spies on western Europe, North Africa and possibly the United States. Although during the Cold War, the height of NS usage was pretty high, it doesn't mean that they aren't used anymore. Locating a signal to listen into these stations is not an easy task. Adept knowledge of Ham Radio usage is needed to circle into a broadcast. The more subtle of the messages are the morse code and polytones broadcast. You can use http://www.w4ax.com to search for some signals on your own.