NOMAD - NUMBERS STATION
Number stations are secret shortwave radio stations that started to appear around World War I. They are characterized by broadcasting strings of seemingly random numbers, often by a recorded voice reading them out, or morse code.
It has long been speculated that these stations operate as a simple method for government agencies to communicate with spies working undercover in foreign countries, however, like expected, no government ever admitted using these stations, and no one has ever been able to crack the codes they send out.
The most famous number station broadcast is probably the "Lincolnshire Poacher". It transmitted from Cyprus from mid 1970's until 2008. You can listen to its eerie signal on wikipedia:
https://en.wikipedia.org/wiki/Lincolnshire_Poacher_(numbers_station)
Number stations are still around and sometimes their broadcast interfere with other radio stations around the world. Few of them has ever been tracked down by location, so we don't have any good idea what they look like. This version is an artistic interpretation of what I think one could have looked like sometime around last mid-century, using the commonly used radio equipment that was manufactered at the time.
