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Flag semaphore

System to transmit information by hand / From Wikipedia, the free encyclopedia

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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. Information is encoded by the position of the flags; it is read when the flag is in a fixed position. Semaphores were adopted and widely used (with hand-held flags replacing the mechanical arms of shutter semaphores) in the maritime world in the 19th century.[2] It is still used during underway replenishment at sea and is acceptable for emergency communication in daylight or using lighted wands instead of flags, at night.[citation needed]

A US Navy crewman signals the letter 'U' using flag semaphore during an underway replenishment exercise (2005)