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A US Navy crewman signals the letter 'U' using flag semaphore during an underway replenishment exercise (2005). Flag semaphore (from the Ancient Greek σῆμα (sêma) 'sign' and - φέρω (-phero) '-bearer' [1]) is a semaphore system conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands.
The Phryctoriae were a semaphore system used in Ancient Greece for the transmission of specific prearranged messages. Towers were built on selected mountaintops, so that one tower, the phryctoria, would be visible to the next tower, usually 30 km (20 mi) distant. Flames were lit on one tower, then the next tower would light a flame in succession.
The International Code of Signals (INTERCO) 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 ("blinker"), flag semaphore, radiotelegraphy, and radiotelephony.
The operators would move the semaphore arms to successive positions to spell out text messages in semaphore code, and the people in the next tower would read them. An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals (a form of optical communication ).
Naval flag signalling undoubtedly developed in antiquity in order to coordinate naval action of multiple vessels. In the Peloponnesian War (431 – 401 BCE) squadrons of Athenian galleys were described by Thucydides as engaging in coordinated maneuvers which would have required some kind of communication; [1] there is no record of how such communication was done but flags would have been the ...
A system like flag semaphore, with an alphabetic code, can certainly send any given message, but the system is designed for short-range communication between two persons. An engine order telegraph , used to send instructions from the bridge of a ship to the engine room, fails to meet both criteria; it has a limited distance and very simple ...
A replica of a Chappe telegraph tower (18th century). A 'semaphore telegraph', also called a 'semaphore line', 'optical telegraph', 'shutter telegraph chain', 'Chappe telegraph', or 'Napoleonic semaphore', is a system used for conveying information by means of visual signals, using towers with pivoting arms or shutters, also known as blades or paddles.
A designator flag is used to indicate if a flaghoist signal is meant to be interpreted as an ICS signal or as a naval signal. The U.S. Navy uses a set of 68 flags, including flags for each letter of the alphabet and each numeral to convey messages of tactical or administrative nature. [2] [better source needed]