Charles Wheatstone



Charles Wheatstone was born in Barnswood, near Gloucester, England, in 1802. Being a shy and sensitive boy he had an early interest in books, be it fairy tales, history or science. His father was a manufacturer and seller of musical instruments, both woodwind and string, with a shop at Pall Mall, London. As a youngster he became an apprentice in his uncle’s musical instruments business. Having access to his father’s tools and materials, in 1818 Charles produced his first musical instrument, the “flute harmonique”, a kind of keyed flute. His interest in musical instruments, sound and acoustics resulted in several instruments: the concertina and the “enchanted lyre”. In 1823 Charles and his brother William took over their uncle’s musical instruments business on his death, but Charles was more interested in devising new or improving existing instruments and he was far less interested in the commercial side of the business. When he came upon a book describing Volta’s discoveries in electricity he started to repeat the experiments described in it, using a home-made battery.

In 1834, Wheatstone was appointed professor in Experimental Physics at King’s College, London, but his extreme shyness in public made him tong-tied and his lectures were no success. He sometimes even turned his back to the audience and just spoke to the diagrams and writings on the blackboard. He had developed a lifelong friendship with the scientist Faraday and quite often it would be Faraday who delivered his lectures and presentations, while Wheatstone restricted himself to performing the actual demonstrations.

Wheatstone became well-known for his measurement of the speed of electricity in a wire. He cut the wire in half so a spark could leap across the gap. The ends of the wire were connected to a Leyden jar with electricity, resulting in three sparks, one at either end and one in the middle. By the ingenious use of a mirror revolving at high speed he demonstrated the lag in time of the spark in the middle of the wire. By measuring this lag and relating it to the speed of the revolving mirror he was able to calculate the speed of electricity at 288,000 miles per second. Later it was found that this speed would also depend on the nature of the conducting material and its resistance.


Wheatstone’s telegraph interrupter

Wheatstone’s importance in the development of the computer stems from his work on the electric telegraph and more specifically his invention of the automatic transmitter for the telegraph in 1857. In this process he partnered with William Fothergill Cooke.

In the past telegraph messages had been sent using the system devised by Samuel Morse, where telegraph operators manually operated the sending key of a transmitter. Wheatstone devised a method of first recording the message on a paper tape using two rows with punched holes. This was significantly faster than the manual system at a speed of about 100 words per minute. Although his method of recording was still based on the traditional Morse code with its dots and dashes, the same text would now occupy a much shorter piece of tape. This, combined with the transport channel in the centre of the tape, resulted in a significant speeding up of the mechanical “reading” process. At the receiving end of the telegraph the paper tape output could be decoded into readable text again by the teleprinter. Although telegraph lines had been in existence for some time it was only in the late 1830s that people like Wheatstone started thinking about undersea telegraph lines and how these cables could be insulated. In 1851 the first successful submarine cable across the English Channel was laid, insulated by gutta percha, a latex material from rubber trees in Malaysia. This resulted in a boom in companies producing and laying cables in all parts of the world. After many unsuccessful attempts the first trans-Atlantic cable was laid in 1866 - the great continents were finally connected.

                                 

Wheatstone tape with piece showing                 Baudot tape with piece showing                Morse tape with
             one character                                                  one character                              dots and dashes



Wheatstone’s system of recording, storing and transmitting information (data) using perforated paper tape would be further enhanced by Baudot, who changed the two rows of punched holes to five rows resulting in a further increase in the speed of reading and processing. Punched paper tapes have been used extensively as input and output medium in the early computers.


Following the completion of his automatic telegraph, Wheatstone was knighted in 1868.


Charles Wheatstone died on October 19, 1875, while on a visit to Paris, France.




                   

Wheatstone tape and telegraph                    Teleprinter                      and its reading mechanism

Teletypes or teleprinters had intricate mechanisms for reading paper tape and printing its contents. This enabled speeds of 500 characters per minute in 1930. By the mid sixties this speed had increased to 900 char/min.


America's financial institutions received their stock exchange information via telex machines which rattled all day with its punched paper tape equipment. The old punched paper tapes and the punched out holes were often used in the famous "ticker tape" parades in America's large cities.




         

Type I                                        Type II

This 1958 USSR stamp features, apart from the teletype in the bottom right corner, a number of flags. The Czechoslovakian flag on the left is upside-down. The flag shows a red strip, a white strip and a blue triangle on the right. The original stamp design is incorrect in showing the red strip at the top (Type I). The stamp was re-issued six months later with the flag positioned correctly (Type II).




Wheatstone Telegram from Wagga Wagga, NSW, Australia (1924) with text in Morse code:
“Black pickles contractors Junee X Glass broken Paul Blamey Please send measurements
your price fixing including cartige we take risk also state value of salvage X Sandy”



© Wobbe Vegter, 2006






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