Electromagnetic telegraph

An electrical telegraph is a telegraph that uses electrical signals, usually conveyed via dedicated telecommunication lines or radio.

The electrical telegraph, or more commonly just telegraph, superseded optical semaphore telegraph systems, such as Claude Chappe's towers designed for communication among the French military, and Friedrich Clemens Gerke for the Prussian military, thus becoming the first form of electrical telecommunications. In a matter of decades after their creation, electrical telegraph networks permitted people and commerce to transmit messages across both continents and oceans almost instantly, with widespread social and economic impacts.

From early studies of electricity, electrical phenomena were known to travel with great speed, and many experimenters worked on the application of electricity to communications at a distance.

All the known effects of electricity - such as sparks, electrostatic attraction, chemical changes, electric shocks, and later electromagnetism - were applied to the problems of detecting controlled transmissions of electricity at various distances.

In 1753 an anonymous writer in the Scots Magazine suggested an electrostatic telegraph. Using one wire for each letter of the alphabet, a message could be transmitted by connecting the wire terminals in turn to an electrostatic machine, and observing the deflection of pith balls at the far end. Telegraphs employing electrostatic attraction were the basis of early experiments in electrical telegraphy in Europe, but were abandoned as being impractical and were never developed into a useful communication system.

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