Music broadcasts were also used to send secret message to hostages in Colombia: https://news.ycombinator.com/item?id=8852772 https://news.ycombinator.com/item?

Music broadcasts were also used to send secret message to hostages in Colombia: https://news.ycombinator.com/item?id=8852772 https://news.ycombinator.com/item?id=8852772