Railroad Signal Telegraphy

The telegraph transformed railroad signaling, making it possible for train operators to send messages ahead of trains for the first time. American inventor Samuel Morse devised the earliest experimental telegraph, and the Cooke and Wheatstone needle telegraph, a later model, first entered commercial use in 1838 when it was adopted by the Great Western Railway in Britain. The system gained wider acceptance after its dramatic role in apprehending British murderer John Tawell in 1845: he had been seen boarding a train at Slough, and this information was telegraphed ahead to Paddington Station, where he was arrested. In 1844, Morse’s telegraph transmitted the words “What hath God wrought” from Baltimore to Washington, DC, and brought about a revolution on the US railroads.

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The needle telegraph

Inventor William Fothergill Cooke and scientist Charles Wheatstone patented their five-needle telegraph in 1837. It consisted of a receiver with needles that were moved by electromagnetic coils to point to letters on a board. Each letter was communicated via two currents flowing down two wires, causing the receiving telegraph’s needles to swing to the left or right. Six letters were omitted—C, J, Q, U, X, and Z—a limitation that caused confusion when identifying the murderer Tawell (see above), who was described as wearing a “KWAKER” (Quaker) coat.

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Morse’s telegraph

Invented in 1835, Morse’s first telegraph used a pencil point attached to an electromagnetic pendulum. His partner Alfred Vail suggested using a lever and armature to print a code of dots and dashes—the precursor to Morse code—sending the message “a patient waiter is no loser” in 1838. This system, patented in 1840, was soon adopted in the US both for railroad signaling and general use, with lines built alongside new railroads. It was cheaper and simpler to use than the needle telegraph, especially once adapted to an audio system.

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