High Quality Content by WIKIPEDIA articles! A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position. These systems were popular in the late 18th to early 19th century. In modern usage, "semaphore line" and "optical telegraph" may refer to a relay system using flag semaphore, and "optical telegraph" may refer to a heliograph (optical telegraphy using mirror-directed sunlight reflections).