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La Roue Phonique.


Copenhague, K. Schønberg, 1878. 8vo. Uncut and unopened in the original printed, illustrated wrappers. A very fine copy of this delicate publication. 72 pp. Many text-illustrations throughout. ¶ Very rare first edition of the first work to describe the seminal invention that is the phonic wheel, invented and patented by Paul la Cour - "the Danish Edison" - in late 1877 and publicized for the first time in 1878 in French (as it is here) and Danish simultaneously. The phonic wheel, a synchronous motor operated by pulsating current, constituted a fundamental improvement upon the telegraph-system, as it enabled the simultaneous sending of up to 100 telegrams at a time (in comparison, Edison, who worked on solving the same problem at the same time, was only able to invent a device allowing for the sending of 4 telegrams at a time). This seminal invention revolutionized the telegraph-system. It was also of great importance to the early development of the television, as it constituted an important feature in proposals for telectroscopes and in some electromechanical television systems. The phonic wheel was the first invention to make use of the principle that we now call "time division multiplexing".

"It was no coincidence that Poul la Cour got the byname "The Danish Edison". Apart from his job as deputy director at the Danish Meteorological Institute, he worked with many inventions e.g. the telegraph system which at the time was undergoing a rapid development. At that stage, only one message could be sent at the time and often the line was busy. This was a great disadvantage especially within the field of meteorology where fast communication over long distances was important.
Poul la Cour worked on a method to let several telegraphists use the same wire simultaneously and in 1874 he was awarded the gold medal from the Danish Scientific Society for his work on the phonic telegraph system. By using this system each telegraphist could send the Morse code through an electric tuning fork and thereby use his own frequency on the same wire.
In 1878, he developed the method into the phonic wheel motor that made it possible to send up to 100 telegrams at the same time. He was in fierce competition with the famous American inventor Thomas A. Edison who only managed to send 4 telegrams simultaneously. The many inventions quickly gave Poul la Cour the byname "The Danish Edison"." (From the web-site of the Paul La Cour Museum)

While working on developing his tuning fork-telegraph, la Cour got the idea of a phonic wheel. He allowed for the oscillations of the tuning fork to control the phonic wheel, giving it a constant and extremely precise circulation. The phonic wheel was a toothed iron wheel; the teeth passed by a electro-magnet, which again was controlled by the electric oscillations from a tuning fork. If one of the teeth of the wheel is right in front of the magnetic pole, it will in turn be attracted to and let go by the magnet. The invention did cause la Cour problems in the beginning, but when he came up with the idea of placing a capsule with quicksilver upon the wheel, it became more stabile. The toothed wheel was now so precise that it was possible to divide the telegraph-current into little bites, so several senders/receivers were able to share the same wire by taking turns sending. Thus, the phonic wheel was the first invention to make use of the principle that we now call "time division multiplexing", i.e. that cables can be used for many purposes at the same time.

After having finished his studies in physics and meteorology in Copenhagen in 1869, Poul la Cour travelled in Europe to study practical meteorology. Having spent a month with the Dutch meteorologist de Buijs Ballot, he became convinced of the importance of setting up the Danish Meteorological Institute according to the principles of de Buijs Ballot, which was set up in 1872, with la Cour as Deputy Director.
At the time, telegraphy was the most important technological prerequisite for modern meteorology, and this soon became la Cour's main interest. In June 1874, the year in which Edison invented his quadruplex telegraphy, la Cour invented a telegraphic device based on tuning forks. He patented his invention in London on September 2, 1874, but in the United States Alexander Graham Bell, Elisha Gray, and others had been working along similar lines, which resulted in protests against his American patent applications. Not wanting to spend the large amount of money necessary to pay the American lawyers, he gave up his claim in America, and this invention was credited to Elisha Gray. La Cour, however, maintained that Gray had been working on the invention of the telephone, and only had changed his invention at the instant la Cour's American application was published.
After the disappointment on the American market, la Cour came up with the seminal invention that was the phonic wheel, and this time there were no problems with the patent. The invention was produced in August 1875, patented in 1877, and the details were published in the book "The Phonic Wheel" in 1878, in a Danish and a French edition. At that time the invention was adopted by the American company The Delany Synchronous multiple Telegraph, and a new fight of priority arose. In 1886 the Franklin Institute awarded la Cour the John Scott Legacy Medal for the phonic wheel and at the same time presented Delany with the Elliott Cresson Medal for the synchronism, a decision la Cour protested against.
The phonic wheel was used on telegraph lines on the East Coast of America, and in the London Post Office. The most modern application was in the mechanical "television" of Paul G. Nipkow (1884).

Shiers: Early Television. A Bibliographic Guide to 1940: No. 102

25 762 SEK

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