NMSAT :: Networked Music & SoundArt Timeline

1874 __ The Baudot printing telegraph, a multiplex system
Jean Maurice Émile Baudot (1845-1903)
Comment : Automatic telegraph linking 4-6 sending/receiving apparata to a single line, invented in France by Jean Maurice Baudot. (Tom Standage)After successively improved versions, he demonstrated at the International Exhibition of Electronics a perfected model which could transmit six simultaneous messages. Being an engineer at the French Telecommunications Service, Emile Baudot was working on a way to improve the efficiency of the then very slow telegraphic transmission. He had to overcome many difficulties, especially the avoidance of timing errors between phases of transmission and reception. Finally he developed what is called "the Baudot printing telegraph". Today it would be called a synchronous time division multiplex system. Baudot invented his telegraph code in 1870. By 1874 or 1875 (various sources give both dates) he had also perfected the electro-mechanical hardware to send his code. Actually, his inventions were based on certain printing details from the Hughes instrument, a distributor invented by Bernard Meyer in 1871, and the five unit code devised by Gauss and Weber. Baudot combined these, together with original ideas of his own, to produce the final multiplex system. ot code is the first truly digital one. It consists of only two states, both logically and electrically. Logically, the only states are "1" and "0". Today we call the unit that can have these two logical states a "bit". Electrically, the states are current flowing (or "1"), and no current flowing (or "0"). Each character consists of 5 bits. Two logical states and five bits allows 32 characters. Baudot needed 26 characters for the alphabet, 10 for numbers, and more for miscellaneous characters. The Baudot system was accepted by the French administration in 1875. The first on-line tests of his system took place between Paris and Bordeaux on November 12, 1877. At the end of 1877, the Paris-Rome line (about 1700 km) began to be served by a double Baudot telegraph system. The first telegrams transmitted were those announcing the election of Mr. Carnot to the presidency of the French Republic. [...] The Baudot transmitters and receivers were substituted purely and simply for the recorder. On August 8, 1890, he assured, on a single wire, discrete relations between the three towns of Paris, Vannes, and Lorient, inaugurating at this date the spread-out posts that were later so much generalized. On April 27, 1894, he established, always over a single wire, communications between the Paris stock exchange and the Milan stock exchange, and at the same time between the central Paris and central Milan, and invented for this occasion the retransmitter. [...] A unit for the speed of telegraph transmission, Baud, was named after Baudot (Baud is short for Baudot). Baud was the prevalent measure for data transmission speed until replaced by a more accurate term, bps (bits per second). One baud is one electronic state change per second. Since a single state change can involve more than a single bit of data, the bps unit of measurement has replaced it as a better expression of data transmission speed. In English, 45.5 baud is about 60 words per minute (wpm). (Compiled from various sources)
French comment : Le problème de la transmission multiple a été résolu de la manière la plus rigoureuse, par le merveilleux appareil qui porte le nom de son inventeur, le télégraphe Baudot, lequel non seulement utilise le travail de plusieurs employés qui se succèdent, mais encore imprime les dépêches. On peut en effet définir le télégraphe Baudot un télégraphe permettant de transmettre à distance et par un seul fil le travail de quatre ou six employés, manipulant à la fois quatre ou six claviers alphabétiques distincts, et permettant de recevoir quatre ou six dépêches, qui s'impriment, à l'arrivée, en caractères typographiques, sur des bandes de papier, qu'il suffit de coller sur une feuille de papier, et de faire parvenir au destinataire, comme dans le système Hughes H. Le nom de télégraphe mutiple imprimeur lui convient donc parfaitement, puisqu'il réalise la transmission multiple, et qu'il imprime la dépêche, à l'arrivée. (Louis Figuier)Le télégraphe imprimant Baudot fut breveté en 1874. Le mécanisme très complexe a été perfectionné par les constructeurs Dumoulin-Froment puis J. Carpentier. Ce télégraphe était conçu pour pouvoir fonctionner en duplex sur une ligne (dans les deus sens). Le manipulateur est un clavier à 5 touches capable de 32 signaux en pressant une ou plusieurs touches simultanément. Jean-Maurice Émile Baudot se signale rapidement en apportant des perfectionnements aux appareils existants et invente un code binaire de transmission, le code Baudot, qui supplante le code morse alors utilisé. En août 1874, il dépose un brevet concernant un télégraphe, rapide et imprimeur permettant quatre transmissions simultanées sur un fil, muni d’un clavier de machine à écrire, qui utilise son code : le télégraphe Baudot. (brevet n°103.898, "Un système de télégraphe rapide") Les premiers essais en ligne de son système ont eu lieu entre Paris et Bordeaux, fin 1877. À l'exposition universelle de 1878, Baudot gagne la grande médaille d'or et les félicitations unanimes des ingénieurs du monde entier. (UTC Compiègne)
Source : Standage, Tom (1998), “The Victorian Internet”, The Berkley Publishing Group, New York, p. 181.
Source : Source: Figuier, Louis (1867-1891), "Supplément au Télégraphe Électrique", In "Les Merveilles de la Sciences ou Description des Inventions Scientifiques depuis 1870 - Supplément", Paris: Jouvet et Cie (Eds), pp. 523-603.
Urls : http://chem.ch.huji.ac.il/history/baudot.html (last visited ) http://gallica.bnf.fr/ark:/12148/bpt6k24678x.image.f527 (last visited ) http://www.utc.fr/~tthomass/Themes/Unites/Hommes/bau/Emile%20Baudot.pdf (last visited ) http://cnum.cnam.fr/CGI/fpage.cgi?P84.4/401/100/432/0/0 (last visited ) http://cnum.cnam.fr/CGI/fpage.cgi?P84.7/546/100/667/0/0 (last visited )

No comment for this page

Leave a comment

:
: