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1878 __ Microphone & Telephone — A sound magnifier
Thomas Alva Edison (1847-1931), Pr David E. Hughes (1831-1900)
Comment : Professor David Edward Hughes reasoned that as the electrical condition of substances is affected by heat, and in some cases at least by light, and that heat and light being undulating motions, therefore the electrical condition should be affected by sound, sound being, as in the other cases, the production of motion. To investigate this he “made a rough-and-ready telephone, with a small bar magnet 4in. long, half the coil of an electro-magnet, and a square piece of ferrotype iron, 3in. square, clamped rigidly in front of one pole of the magnet between two pieces of board.” [...] In the ordinary telephone the sound wave is made to impinge upon a diaphragm which causes magnetic changes in a permanent magnet, and electrical changes in the coil surrounding the magnet, but Professor Hughes dispenses with the diaphragm. You speak at the French nails, or the tubes prepared, and the sonorous waves directly effect the required result. The following experiments can easily be made. Take a prepared tube and fasten it on the top of an empty money box with one end taken out, speak or sing into the box, and the sound is reproduced clear and distinct on the receiving telephone – Bell’s. Nay, you need not speak into the box, put the box to your ear, or your forehead, or your foot if you like, and talk away – the sound is transmitted all the same. Speak to the coin and the sound traverses the circuit to the ear at the distant telephone. But these extraordinary results rapidly pale before others more wonderful still. The apparatus which has been termed a microphone, consists solely of a piece of metallized carbon, balanced on a pivot and connected with one pole of the battery through the telephone; this piece of carbon can rest on another piece of metallized carbon connected with the other pole of the battery. [...] Sixpence and sixteen minutes’ attention would enable any one to make this wonderful microphone. Speak to it a yard away and the sound is conveyed with distinctness; touch the wood upon which it rests with the softest camel’s hair brush and you have the sound of sawing wood at the receiving end; touch with the holder of the brush and you hear the harsh grating sound as if carpenters were sharpening their saws; take prisoner a common house fly, incarcerate him in a match-box surrounded with gauze, and place the prisoner in his prison-house near the microphone, and with ear at the telephone you hear him tramp as he walks. This instrument is destined to prove of the utmost importance in the hands of the physician. The noises in the chest, the beatings of the heart, will all be laid bare with a distinctiveness never before known and hardly ever conceived. This, indeed, seems to approach the confines of perfection. You need not trouble to be within a foot or a yard of the instrument. It is a verbatim reporter. A speaker might have a score or so of such reporters before him connected electrically with the principal towns in the kingdom, and his words would be repeated distinctly. The ordinary voice if too near sounds harsh and disagreeable. There is an old saying that “Walls have ears,” and it is now so far true that double doors and walls cannot keep secret any conversation held within. A singular fact about the whole of these experiments is that the people at both ends of the line may be talking or singing simultaneously, and the conversation or song is transmitted without interference to the other end, but you do not hear your own speech or song at your own telephone. Here then we can have a duplex system without any special apparatus, and probably it will be found that not only two, but many times two, messages are capable of being transmitted at the same time. (THE ENGINEER, MAY 17,1878, PROFESSOR D. E. HUGHES’S TELEPHONE, MICROPHONE, AND THERMOPILE)The years 1876-8 will be distinguished in the history of our time for a triad of great inventions which, so to speak, were hanging together. We have already seen how the telephone and phonograph have originated; and to these two marvellous contrivances we have now to add a third, the microphone, which is even more marvellous, because, although in form it is the simplest of them all, in its action it is still a mystery. The telephone enables us to speak to distances far beyond the reach of eye or ear, 'to waft a sigh from Indus to the Pole; 'the phonograph enables us to seal the living speech on brazen tablets, and store it up for any length of time; while it is the peculiar function of the microphone to let us hear those minute sounds which are below the range of our unassisted powers of hearing. By these three instruments we have thus received a remarkable extension of the capacity of the human ear, and a growth of dominion over the sounds of Nature. We have now a command over sound such as we have over light. For the telephone is to the ear what the telescope is to the eye, the phonograph is for sound what the photograph is for light, and the microphone finds its analogue in the microscope. As the microscope reveals to our wondering sight the rich meshes of creation, so the microphone can interpret to our ears the jarr of molecular vibrations for ever going on around us, perchance the clash of atoms as they shape themselves into crystals, the murmurous ripple of the sap in trees, which Humboldt fancied to makecontinuous music in the ears of the tiniest insects, the fall of pollen dust on flowers and grasses, the stealthy creeping of a spider upon his silken web, and even the piping of a pair of love-sick butterflies, or the trumpeting of a bellicose gnat, like the 'horns of elf-land faintly blowing’. [...] To connect the microphone up for use, a small voltaic battery, say three cells (though a single cell will give surprising results), and a Bell speaking telephone are necessary. A wire is led from one of the carbon brackets to one pole of the battery, and another wire is led from the other bracket to one terminal screw of the telephone, and the circuit is completed by a wire from the other terminal of the telephone to the other pole of the battery. If now the slightest mechanical jar be given to the wooden frame of the microphone, to the table, or even to the walls of the room in which the experiment takes place, a corresponding noise will be heard in the microphone. By this delicate arrangement we can play the eavesdropper on those insensible vibrations in the midst of which we exist. If a feather or a camel-hair pencil be stroked along the base-board, we hear a harsh grating sound; if a pin be laid upon it, we hear a blow like a blacksmith's hammer; and, more astonishing than all, if a fly walk across it we hear it tramping like a charger, and even its peculiar cry, which has been likened, with some allowance for imagination, to the snorting of an elephant. Moreover it should not be forgotten that the wires connecting up the telephone may be lengthened to any desired extent, so that, in the words of Professor Hughes, 'the beating of a pulse, the tick of a watch, the tramp of a fly can then be heara hundred miles from the source of sound.' [...] The applications of the microphone were soon of great importance. Dr. B. W. Richardson succeeded in fitting it for auscultation of the heart and lungs; while Sir Henry Thompson has effectively used it in those surgical operations, such as probing wounds for bullets or fragments of bone, in which the surgeon has hitherto relied entirely on his delicacy of touch for detecting the jar of the probe on the foreign body. There can be no doubt that in the science of physiology, in the art of surgery, and in many other walks of proved a valuable aid. [...] We need not be surprised that the microphone should not only act as a TRANSMITTER of sounds, but that it should also act as a RECEIVER. Mr. James Blyth, of Edinburgh, was the first to announce that he had heard sounds and even speech given out by a microphone itself when substituted for the telephone. His transmitting microphone and his receiving one were simcinders from the grate. (John Munro)“PROFESSOR D. E. HUGHES’S TELEPHONE, MICROPHONE, AND THERMOPILE” -- THE various branches of physical science are so inter-connected that any important discovery in one branch is frequently the forerunner of a number of discoveries not only in that particular direction, but in cognate branches. Such has been the case as regards the researches and discoveries of Reiss, Gray, Edison, and Bell. The human mind, having its energies once turned in a certain direction, does not remain satisfied until it meets with an impenetrable blank- not, however, to remain a blank for ever, but only until other discoveries give the means to overcome difficulties. Nature has long ago learned how to bottle-up the sunshine and hide it in the bowels of the earth till toiling man claims the treasure, and utilizes anew the long, long pent-up force. Man is now emulating nature, and bottles up sound to reproduce at his own convenience. Her results, however, can only be obtained by acting in accordance with Nature’s laws. A new discovery, then, means the discovery of a new law or a new application of an old law. Physicists have long agreed that heat and sound are modes of motion. Heat, however, cannot be observed unless the matter in motion impinges on a material object whose molecules have not the same motion. Similarly sound is only heard when the motion is capable of actuating the organs of the ear. The introduction of the telephone has given an impetus to the study of vocal sounds, and the researches of Prof. Fleeming (sic) Jenkin and others lead us to hope, as Mr. A. J. Ellis says, “that we have at last got an instrument which will enable us to solve the elementary problems of phonetics that have hitherto almost baffled us, although it is not suited, as yet, to fix those delicacies of utterance which were my own special object of investigation.” As we proceed with this article we shall see that the discovery of Professor Hughes has given Mr. Ellis a far more delicate instrument than that of Professor Bell, and thus the investigation into the laws of acoustics can be carried further. Professor Hughes reasoned that as the electrical condition of substances is affected by heat, and in some cases at least by light, and that heat and light being undulating motions, therefore the electrical condition should be affected by sound, sound being, as in the other cases, the production of motion. To investigate this he “made a rough-and-ready telephone, with a small bar magnet 4in. long, half the coil of an electro-magnet, and a square piece of ferrotype iron, 3in. square, clamped rigidly in front of one pole of the magnet between two pieces of board.” Professor Hughes is justified in calling attention to what he terms rough-and-ready apparatus. Old match-boxes, money-boxes, empty cigar boxes, and pieces of material that most philosophers would despise, have in his hands been fashioned and manipulated to give astounding results. (In “THE ENGINEER”, MAY 17,1878)A "watcher" during the first alf of that year, 1878, must have risen early to keep pace with Edison. He was "here, there and everywhere". The microphone, the megaphone and the aerophone were added in rapid succession to the phonograph family. When David E. Hughes, an able inventor who had gone from America, revealed that he had developed a sound magnifier which he called the microphone, Edison pronounced it "a straight steal" of his carbon transmitter principle : "After I sent one of my young men over to London especially to show Preece the carbon transmitter, and where Hughes first saw it and heard it, then within a month he comes out with the microphone without any acknowledgment whatever. Published dates will show that Hughes came along after me. As soon as he read this, W.H. Preece, electrician of the British post-office, cabled to the "Scientific American", "most absolute and unqualified denial". Everybody was agog over the possibilities of this new device. It would enable them to hear a fly walk ! The passage of a delicate camel's hair brush was magnified to the roar of a mighty wind ! The footfalls of a tiny gnat sounded like the tramp of Rome's cohorts ; the ticking of a watch could be heard more than one hundred miles. (They would have been more astounded had some one told them of how the "mike" was to be used fifty years later in broadcasting). (William Adams Simonds, "Edison - His Life, His Work, His Genius", Chap. 12, “Farewell to Privacy - April-August 1878”, pp. 126-127)
French comment : Essai de transmission (?) sans fil par Hughes au moyen d'un microphone. (In "Encyclopedia Britannica" 2è éd. art. "Hughes" et commentaire de J. Cazenobe in "Les origines de la télégraphie sans fil" 1981)En Mai 1878 , David Hughes (ancien professeur de musique) invente le microphone formé de crayons de charbons cylindriques, dont Thomas Edison lui dispute la paternité dans une campagne de presse. Les microphones à charbon étaient autrefois utilisés dans les combinés téléphoniques ; ils sont moins voire plus du tout utilisés de nos jours. Ce sont aussi les premiers microphones des stations radios telles que la BBC. Ils sont composés d'une capsule contenant des granulés de carbone entre deux plaques métalliques servant d'électrodes. La vibration due à l'onde sonore vient comprimer les granules de carbone. Le changement de géométrie des granules et de leur surface de contact induit une modification de la résistance électrique, produisant ainsi le signal. Ces microphones fonctionnent sur une plage de fréquence limitée et produisent un son de basse qualité mais sont cependant très robustes. (Compiled from various sources)David Hughes nait à Londres et grandit aux Etats-Unis. Il enseigne la musique et étudie l'acoustique au Collège St. Joseph, dans le Kentucky. En 1855, il dépose son premier brevet américain pour une imprimante utilisée avec un instrument de télégraphique. En 1857, Hughes retourne à Londres emportant avec lui son téléscripteur, qui est utilisé jusque dans les années 1930. David Hughes découvre qu'un mauvais contact dans un circuit comprenant une pile électrique et un écouteur de téléphone, permet de reproduire les sons. C'est ainsi qu'en mai1878, il conçoit un microphone constitué d'un crayon de graphite moulé, taillé en pointes aux extrémités et placé verticalement, entre deux petits blocs de charbon, contre une planchette verticale. Selon un contemporain le principe est simple “le tic-tac d'une montre fait vibrer légèrement la planchette ; les points de contact du charbon se déplacent et le courant électrique subit des perturbations qui se traduisent par des vibrations sonores dans le téléphone” (De Parville). (Denis Roque)Le microphone à charbon a permis un véritable dévellopement du téléphone et une utilisation plus facile. Sur les premiers téléphones, le dispositif commun à l'émission et à la réception induisait un courant peu élevé, si bien que la voix était reproduite très faiblement. L'utilisation du microphone à charbon, mis au point en 1877 par l'ingénieur américain David Edward Hughes, permit de pallier ce défaut, et de réaliser de ce fait le premier téléphone véritablement opérationnel. Ce type d'appareil, toujours utilisé, comprend un émetteur composé de deux plaques métalliques entre lesquelles est placée de la grenaille de charbon. L'une des plaques fait office de diaphragme, transmettant aux grains de charbon les variations de pression dues aux ondes sonores. Ces variations entraînent alors une modification de la résistance électrique entre les deux plaques, amplifiant ainsi l'énergie captée et donc le volume de la voix. Malheureusement, le principe de ce microphone ne permet pas de convertir les signaux électriques en variations de pression, si bien que les téléphones utilisant ce système sont équipés de récepteurs séparés des émetteurs. Cette disposition permet par ailleurs de placer le microphone près de la bouche et l'écouteur près de l'oreille, ce qui rend l'appareil plus pratique. (Nicolas ls, 1999)
Source : Munro, John (1891), “Heroes of the Telegraph”, Published by BiblioBazaar, 2008, Chapter 10, pp. 201-202 ; and also :Published by Icon Group International Inc (Webster’s French Thesaurus Edition), pp. 186-187.
Source : Simonds, William Adams (1934), "Edison - His Life, His Work, His Genius", First Edition, Brooklyn New York : Braunworth and Co. Inc.
Urls : http://www.worldwideschool.org/library/books/tech/engineering/HeroesoftheTelegraph/chap10.html (last visited ) http://telephoniste.free.fr/historique/ (last visited ) http://members.multimania.co.uk/MikePenney/hughes.htm (last visited ) http://fredouille.pagesperso-orange.fr/creation.htm (last visited ) http://forums.futura-sciences.com/electronique/242063-fonctionnement-touts-1er-telephones.html (last visited ) http://pdf.directindustry.fr/pdf/aet/telephonie-industrielle/7632-27683-_14.html (last visited ) http://nlsn.free.fr/telecom/pages/texte/hist-tel.html (last visited ) http://cnum.cnam.fr/CGI/fpage.cgi?P84.1/30/100/248/0/0 (last visited )

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