Secret Signals via Mainstream Media

During World War II the BBC cooperated with the intelligence services to send open code signals to operatives in the occupied territories. These signals were prearranged with the operatives, and then sent out at two scheduled times. This signalling channel was used exclusively for indicating whether an operation was going to take place.

The BBC would broadcast the signal for the first time at 1930, and then confirm the signal at 2115. If the operation had been canceled before the second scheduled signal window, the code phrase would not be repeated.

During the early phase of the war, the code system was slightly more complex. There would be a positive code, and a negative code, for example: “Jeanne sends her greetings” might be a “go code”, and “Jeanne says hello” might be the “abort code”. Later this was simplified to just the positive code (a tradition that, apparently, the CIA still follows).

More to follow.