Bridging distance through telegraphy

Charles Wheatstone is perhaps most widely known for a device which he did not, in fact, invent: the Wheatstone bridge. Rather, he popularized practical use of an instrument developed by Samuel Hunter Christie in 1833, which Wheatstone realized could be used to measure the electrical resistance of a circuit. Nevertheless, Wheatstone was an important innovator who created the world’s first public telegraph system. And to answer the question posed in September’s Pioneers’ Page, he was also the inventor of a popular musical instrument, the concertina.

The scientist invented the forerunner of the concertina,
the “Symphonium,” in 1829, and patented the concertina itself in 1844.

A musical background

Wheatstone was born into a musical family in 1802, in Gloucester in the west of England. After they moved to London, Charles was apprenticed in the family music shop. He helped to attract business by making an “Enchanted Lyre” which astonished customers by emitting the sounds of various musical instruments. In fact, the “telephonic” lyre was simply a sounding box suspended from a solid rod connected to instruments played out of sight on the floor above.

In 1823, Wheatstone proposed that a communications system be constructed between London and Edinburgh using sound transmitted through rods. However, it was the electrical production of signals that was to be the next focus of his research. Wheatstone became Professor of Experimental Physics at King’s College, London, in 1834 — the first person to hold that position. In the same year, he achieved fame when he made the first-ever measurement of the speed of electricity in a wire.

Schilling, Cooke and Wheatstone

There had been experiments with sending signals using electricity since the mid-18th century. Practical proposals only became possible, though, after the discovery by Hans Christian Øersted in 1820 that an electric current can deflect a magnet. This principle was employed by Baron Pavel Lvovitch Schilling, a Russian diplomat and engineer who, in 1832, made the world’s first electromagnetic telegraph, linking two rooms inside his home in St Petersburg. An Englishman, William Fothergill Cooke, heard about this invention in 1836 and became keen to commercialize it.

Cooke (1806–1879) tried designing a telegraph system, but could not make it work. He therefore proposed a partnership with Wheatstone, who could provide the scientific skills while Cooke contributed his business acumen. Wheatstone had already been working on an electromagnetic telegraph system and, in June 1837, the two men filed a joint patent in London. Their device used five needles, two of which were moved when a key completed or broke a circuit in a battery, sending electricity down the wire to an electromagnet at the other end. The deflected needles pointed to letters of the alphabet.

A double-needle telegraph in an ornate case, reputedly
used for signaling directly to buckingham Palace in London

An experimental telegraph line, about 2.5 km long, was laid alongside railway tracks in north London. On 25 July 1837, Wheatstone sent the first message and Cooke replied. Wheatstone later recalled that “never did I feel such a tumultuous sensation before, as when, all alone in the still room, I heard the needles click and, as I spelled the words, I felt all the magnitude of the invention pronounced to be practicable beyond cavil or dispute.”

Capturing a world first

The system was used to create the world’s first commercial telegraph line in 1839, covering some 22 km along the Great Western Railway from London. It was extended in 1841, and the innovation was advertised as a public attraction. However, what really drew people’s attention to the potential of telegraphy was the capture of a murderer on 1 January 1845. John Tawell had killed his lover, Sarah Hart, in a town near the railway. To escape, he took a train to London. He might have succeeded, had not the police used the new telegraph to signal his description to the terminus. On his arrival, Tawell was arrested. He confessed to the crime and was subsequently hanged.

Moving to Morse  

The five-needle telegraph had the advantage of not requiring a skilled operator, but it needed multiple circuits and this meant higher installation and maintenance costs. Wheatstone and Cooke made the device simpler, introducing a double-needle and then a single-needle telegraph. These needed skilled operators as they used a complex code to identify letters, based on deflections of the needles. By 1848, some 1600 km of railway were equipped with telegraph wires carrying messages from London to over 200 towns and cities across the United Kingdom.

Meanwhile, in the United States, Samuel Morse and Alfred Vail had also been working on electromagnetic telegraphy since the mid-1830s. Their system first went into operation in 1844 and marked a paper tape to show when electric current — and a message — was transmitted along a single wire. The “Morse code,” patented in 1840, allowed the paper “dots” and “dashes” (and later sounds) to be translated into text. This simpler code than Wheatstone’s was eventually adopted as the international standard for sending messages.

In the five-needle telegraph, two needles
at a time were deflected to point at a letter.    

Wheatstone also studied the possibility of laying telegraph lines below the sea. In 1840, he proposed such a link between Dover and Calais, and later conducted practical experiments. He was also an expert advisor on the laying of the first transatlantic telegraph line.

 The world’s first telegraph line followed the railway

 A legacy for computers

In 1841, Wheatstone patented a type-printing telegraph — the first of its kind — which used electric current to make a hammer press a letter onto paper. Later, he invented the automatic transmitter, which increased fivefold the number of words that could be sent per minute in Morse code. This was done by replacing the hand of the telegraph operator with a paper tape that had the code punched into it. This passed through a mechanism that controlled signal currents. Early computer designs followed this example by using punched paper tape to input data. In this way, Wheatstone helped to link the world of telegraphy with today’s information age.

Source: ITU NEWS Magazine
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