Signal Flag Letter "S" 3' X 3' (#7) w/toggles

"My engines are going astern."

The International Code of Signals is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters. Signals can be sent by flaghoist, signal lamp, flag semaphore, radiotelegraphy, and radiotelephony.

A complete set of code flags consist of 40 flags: 26 alphabetics, 11 numeric and procedural  pennants, and 3 substitutes.

To make full use of the system, the book Pub102 International Code of Signals is recommended.  See in Professional/Bridge.