Many of the codepoints of flag semaphore match those of the Foy-Breguet electrical telegraph, also descended from the French optical telegraph. Field of Santa Clara University, "there is evidence" that Popham based his telegraph on the French coastal stations used for ship-to-shore communication. Flag semaphore provided an easy method of communicating ship-to-ship or ship-to-shore when the distances were not too great. Such a system was inconvenient to install on board a ship. The land system consisted of lines of fixed stations (substantial buildings) with two large, moveable arms pivoted on an upright member. At this point, sender and receiver change places.įlag semaphore originated in 1866 as a handheld version of the optical telegraph system of Home Riggs Popham used on land, and its later improvement by Charles Pasley. The receiver can reply with the "Attention" signal. The sender ends the transmission with the "Ready to receive" signal. The receiver raises both flags vertical overhead and then drops them to the rest position, once only, to grant permission to send. The receiver uses a "Ready to receive" signal not shown above to grant permission to begin the transmission. The sender uses the "Attention" signal to request permission to begin a transmission. Letters can be signaled by first signaling "J". Numbers can be signaled by first signaling "Numerals".
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