Aboatswain's call, pipe, or bosun's whistle is a pipe or a non-diaphragm type whistle used on naval ships by a boatswain.
The pipe consists of a narrow tube (the gun) which directs air over a metal sphere (the buoy) with a hole in the top. The player opens and closes the hand over the hole to change the pitch. The rest of the pipe consists of a "keel", a flat piece of metal beneath the gun that holds the call together, and the "shackle", a keyring that connects a long silver or brass chain that sits around the collar, when in ceremonial uniform.
Historically the boatswain's call was used to pass commands to the crew when the voice could not be heard over the sounds of the sea. Because of its high pitch, it could be heard over the activities of the crew and bad weather. It is now used in traditional bugle calls such as Evening Colors/Sunset, and in other ceremonies in most modern navies. It is sometimes accompanied by other auditive features such as ruffles and flourishes, voice commands and announcements, or even a gun salute.
It was first used as a badge of rank for the Lord High Admiral of England in 1485.
The following are the commands that are passed with the help of a bosun's pipe.[2]
