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Concept
Electrical telegraph
Summary
Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems called telegraphs, that were devised to communicate text messages quicker than physical transportation. Electrical telegraphy can be considered to be the first example of electrical engineering.
Text telegraphy consisted of two or more geographically separated stations, called telegraph offices. The offices were connected by wires, usually supported overhead on utility poles. Many different electrical telegraph systems were invented, but the ones that became widespread fit into two broad categories. The first category consists of needle telegraphs in which a needle pointer is made to move electromagnetically with an electric current sent down the telegraph line. Early systems used multiple needles requiring multiple wires. The first commercial system, and the most widely used needle telegraph, was the Cooke and Wheatstone telegraph, invented in 1837. The second category consists of armature systems in which the current activates a telegraph sounder which makes a click. The archetype of this category was the Morse system, invented by Samuel Morse in 1838. In 1865, the Morse system became the standard for international communication using a modified code developed for German railways.
Electrical telegraphs were used by the emerging railway companies to develop train control systems, minimizing the chances of trains colliding with each other. This was built around the signalling block system with signal boxes along the line communicating with their neighbouring boxes by telegraphic sounding of single-stroke bells and three-position needle telegraph instruments.
In the 1840s, the electrical telegraph superseded optical telegraph systems, becoming the standard way to send urgent messages.
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