Here's a trailer for THE NUMBERS STATION, starrting John Cusack and Malin Akerman (WATCHMEN, ROCK OF AGES) and due in theaters April 18.  

Believed to be an overt-but-planned and coded means for intelligence communities to communicate with operatives, Numbers Stations first appeared shortly after World War II and 'were using a format that had been used to send weather data during that war' (per THIS Wiki entry).  Here's an embed featuring a transmission of one Numbers Station,  nicknamed "Lincolnshire Poacher", which has allegedly been traced to a Royal Air Force base in Cyprus.