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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.
At first it was used concurrently with the old system until 1 January 1902, and then used exclusively after 1 January 1903. In this new edition, the number of flags was increased from 18 flags plus a code pennant to 26 flags and a code pennant. The eight new flags represented the vowels A E I O U and the letters X Y Z. [2]
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 ...
Flag semaphore signalling uses two flags, held in specific positions to signify letters. This method requires simple equipment but can be obscured by bad weather. This method requires simple equipment but can be obscured by bad weather.
Signal flags Semaphore Manual alphabet Braille system No/other lang value: Radio alphabet: Morse code: Signal flag: Semaphore: Manual alphabet (fingerspelling) Braille: American NATO phonetic: Morse code: Signal flag: Flag semaphore: American manual alphabet (ASL fingerspelling) Unified English Braille: English NATO phonetic: Morse code: Signal ...
Flag signalling was widely used for point-to-point signalling prior to the optical telegraph, but it was difficult to construct a nationwide network with hand-held flags. The much larger mechanical apparatus of the semaphore telegraph towers was needed so that a greater distance between links could be achieved.
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 ...