telegraph

The telegraph is a system for transmitting messages over long distances by signaling. The name derives from Greek tele "far" and graphein "to write." Telegraphy uses devices and networks that convert a message into signals sent via wires, air, or line-of-sight, then translated back into text at the destination. The two major historical forms are optical semaphore telegraphy and electric telegraphy.

Optical telegraphy, or semaphore, relies on line-of-sight signals relayed between towers. The best-known version was devised by Claude Chappe in France beginning in 1792, using movable arms to form codes that could be relayed across a corridor of towers. Weather, terrain, and maintenance limited range and reliability.

Electric telegraphy uses electrical signals transmitted over wires. In Britain, William Cooke and Charles Wheatstone demonstrated a practical system in 1837; in the United States, Samuel Morse and Alfred Vail developed Morse code and a working telegraph, with a line opened in 1844 between Washington, D.C., and Baltimore. Global networks grew through relay stations and submarine cables, culminating in the transatlantic cable of 1866.

Telegraphy transformed communication, journalism, commerce, and military command by enabling near real-time messages over long distances. It spurred standardized time, rail and ship scheduling, and rapid dispatch of information. The electric telegraph declined with the spread of telephone and digital networks, but its legacy influenced later telex, fax, and data-communications technologies.

The term remains a historical descriptor for early long-distance signaling and its role as a foundational step in modern telecommunications.