Optical telegraph

The optical telegraphs precede the electrical telegraph. It is faster than riding couriers for bringing a message over long distances. Types of optical telegraphs are the semaphore, [ship flags]?, smoke signals, and beacons. The distance that an optical telegraph can bridge is limited by geography, the shape of the earth, and the sharpness of the human eye. In practical use, most optical telegraphs used relay leagues to bridge longer distances.