![]() Morse code receiver, recording on paper tape In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer. ![]() Carl Friedrich Gauss and Wilhelm Eduard Weber (1833) as well as Carl August von Steinheil (1837) used codes with varying word lengths for their telegraph systems. They obtained an English patent in June 1837 and demonstrated it on the London and Birmingham Railway, making it the first commercial telegraph. William Cooke and Charles Wheatstone in Britain developed an electrical telegraph that used electromagnets in its receivers. By making the two clicks sound different with one ivory and one metal stop, the single needle device became an audible instrument, which led in turn to the Double Plate Sounder System. In Morse code, a deflection of the needle to the left corresponded to a dit and a deflection to the right to a dah. However, it was slow, as the receiving operator had to alternate between looking at the needle and writing down the message. Many of the earliest telegraph systems used a single-needle system which gave a very simple and robust instrument. Pulses of electric current were sent along wires to control an electromagnet in the receiving instrument. Length and timing of the dits and dahs are entirely controlled by the telegraphist.įollowing the discovery of electromagnetism by Hans Christian Ørsted in 1820 and the invention of the electromagnet by William Sturgeon in 1824, there were developments in electromagnetic telegraphy in Europe and America. The signal is "on" when the knob is pressed, and "off" when it is released.
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