The electrical telegraph, or more commonly just telegraph, superseded optical semaphore telegraph systems, thus becoming the first form of electrical telecommunications. In a matter of decades after their creation in the 1830s, electrical telegraph networks permitted people and commerce to transmit messages across both continents and oceans almost instantly, with widespread social and economic impacts.
The first commercial electrical telegraph, the Cooke and Wheatstone telegraph, was co-developed by William Fothergill Cooke and Charles Wheatstone. In May 1837 they patented a telegraph system which used a number of needles on a board that could be moved to point to letters of the alphabet. The patent recommended a five-needle system, but any number of needles could be used depending on the number of characters it was required to code. A four-needle system was installed between Euston and
Cooke and Wheatstone had their first commercial success with a system installed on the Great Western Railway over the 13 miles (21 km) from Paddington station to West Drayton in 1838, the first commercial telegraph in the world. This was a five-needle, six-wire system. The cables were originally installed underground in a steel conduit. However, the cables soon began to fail as a result of deteriorating insulation and were replaced with uninsulated wires on poles. As an interim measure, a two-needle system was used with three of the remaining working underground wires, which despite using only two needles had a greater number of codes. But when the line was extended to
From this point the use of the electric telegraph started to grow on the new railways being built from
As well as the rapid expansion of the use of the telegraphs along the railways, they soon spread into the field of mass communication with the instruments being installed in post offices. The era of mass personal communication had begun.
An early successful teleprinter was invented by Frederick G. Creed. In
By the 1930s teleprinters were being produced by Teletype in the
With the invention of the teletypewriter, telegraphic encoding became fully automated. Early teletypewriters used the ITA-1 Baudot code, a five-bit code. This yielded only thirty-two codes, so it was over-defined into two "shifts", "letters" and "figures". An explicit, unshared shift code prefaced each set of letters and figures.
By 1935, message routing was the last great barrier to full automation. Large telegraphy providers began to develop systems that used telephone-like rotary dialling to connect teletypewriters. These machines were called "Telex" (TELegraph EXchange). Telex machines first performed rotary-telephone-style pulse dialling for circuit switching, and then sent data by ITA2. This "type A" Telex routing functionally automated message routing.
The first wide-coverage Telex network was implemented in
At the rate of 45.45 (±0.5%) baud — considered speedy at the time — up to 25 telex channels could share a single long-distance telephone channel by using voice frequency telegraphy multiplexing, making telex the least expensive method of reliable long-distance communication.
Automatic teleprinter exchange service was introduced into