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'.
