HISTORY: "As far as English ships are concerned, the call can be traced back to the days of the Crusades, 1248 AD.  As far back as 1485 AD, it was used by English as an honored badge of rank and was the worn by the Lord High Admiral of England.  It was probably worn because it has always been used as a method of passing orders. . . In our Navy it is often referred to as a 'boatswain's pipe.'"

source: The Bluejackets' Manual 1943, United States Naval Institute

All hands signal	All Hands	A general call to any event in which all hands are to participate. Also used for first, mid and morning watches.
Heaveard signal	Heaveard	"Heave around" on the capstan or winch.
Messcall signal	Mess Call	The pipe "Mess call" is the longest of the lot; it should cover not less than a minute. It consists of "All hands," a long "Heave around," and a long "Pipe down," in that order.
Belay signal	Belay	A short "Belay" means "Vast heaving." A long "Belay" means "Vast heaving and make her fast." Also used to annul an order just passed.
	Bosunb
Password signal	Pass The Word	Piped to command silence preliminary to passing an order or information.