A couple of interesting articles on "Numbers Stations", short-wave radio stations that broadcast strings of numbers, presumably to be decoded by spies in the field.
Link: NPR - 2010 & NPR 2000
A couple of interesting articles on "Numbers Stations", short-wave radio stations that broadcast strings of numbers, presumably to be decoded by spies in the field.
Link: NPR - 2010 & NPR 2000