[D8848AFE], Letter from Charles Dion to Charles Augustus Cheever, December 14th, 1888
[D8848AFE], Letter from Charles Dion to Charles Augustus Cheever, December 14th, 1888
"I duly received, on the 10th inst; your favor of 30th Nov. and I lose no time in sending you the informations you have been asking for. ### What you saw some years ago was not exactly my present Echophone by the instrument leaind to it. The principle of the invention was there but not the complete application of it. What you saw was this: By means of a certain amount of tension exercised upon a diaphragm about 10 inches diameter (said tension obtained through a screw-thread cut within the lid of a cover) and by placing a pan at the spot occupied by the stile of a phonograph, I succeeded in obtaining such powerful vibrations that they were reproduced upon paper by the pen fed with ink. I had only to draw pretty briskly a band of paper in front of the pen and by speaking or singing upon the diaphragm, the vibrations of the voice were neatly and accurately transferred upon the paper. This was all I did in your presence but you appeared quite satisfied with it, and you made the observation that the same arrangement might be applicable to the telephone, which was quite right. ### Then I said to myself that beign able through tension applied to a diaphragm--which tension actually increased the vibrations of the human voice in their true shape and amplitude upon paper, I must have no idfficulty in reproducing the sounds of the voice, either speaking or singing, and this I now feel no hesitation in saying that I am usre to do with a properly constructed apparatus. ### The only reason why Edison did not reproduce accurately the sounds of the voice in his first phonograph was that 1' owing to the stiffness and consequent resistence of his tin foil the vibrations of his diaphragm could not be sufficiently incrusted in it; 2' that owing to his spring interfering with the vibrations of his diaphragm on its center, the diaphragm itself did not vibrate properly, and the consequence of both these defects was that the vibations were not incrusted. The tinfoil in their real amplicted and the sounds of the voice were imperfectly rendered by the instrument. You can no more get the sounds of the human voice without reproducing its vibrations than you can hear the real sound of the piano if you diminish in any way the vibrations of its strings. Suppose the vibrations of the voice to be as large as this: [drawing of waves] and that owing to a defect in your arrangement you can only get them so [drawing of smaller waves] you will never have the real sounds of the voice and this was precisely what Edison was doing with his tinfoil which was too hard to receive accurate incrustations. I know that he has lately brought important modifications in his phonograph and that he now reproduces prety accurately the sounds of the voice, but they are still so feeble that you have to employ tubular receptors to hear them. They cannot be heard simultaneously all over a room by a number of persons at the same time. This must be due to the interference of his central spring with the vibrations of his diaphragm, and perhaps also to his mode of producing the tension of the latter. My system is not open to these objections. My diaphragm vibrates freely upon its center and my arrangement for producing the tension of the diaphragm works to perfection so with my particular combination of parts I feel perfectly sure to incrust the vibrations in their real amplitude in the plastic matter of the revolving cylinder and then to cause the sounds to be drawn out of my Echophone to be heard by all the people in a room without the use of receptors of any kind. ### The arrangement of my diaphragm is different from that of Edison. Should the latter have applied tension to his diaphragm I have applied to my own long before him. When you saw me reproducing the vibrations of the voice upon paper it was through tensions exercised upon my diaphragm and Edison did not think of it at that time. So I am the first inventor of the application of tension to a diaphragm. My system to incrust the vibrations on a plastic matter differs from tht of Edison. He incrusts his vibrations upon a plastic matter evenly spread upon his cylinder. The way I do it is this. I trace a screw thread on the plastic matter of my revolving cylinder. Then my stile, instead of terminating in a point terminates so [diagram], more or less wide. The vibrations of the diaphragm cuase it to break up the top of the thread of the screw and they are kept there in their true shape. To insure the best possible result I keep the stile tip to a certain degree of heat, either with a lamp and proper arrangement, or through an electric current. By thismeans the stile finds no resistance at all in the plastic matter. The advantage of this arrangement is that should the stile be a little too hot the plastic mater will be made to flow on each side of the thread in the space between the two and will in no way interfere with the incrustations made by the vibrations. ### The experiments I have made here have fully demonstrated that the diaphragm must not be made with any metal. Edison employs gold-heater's shin [?]. This also is defective because a certain amount of moisture in the air, or in the atmosphere of a room, will diminish its vibratory power. Mica is the only matter to be employed because heat or moisture will not affect it. And this led me to the following most important conclusion. The body of the instrument must not be made with metal because the least expansion or contraction of the metal under a colder or warmer atmosphere interferes at once with the vibratory power of the diaphragm on account of the change produced in its normal tension. This is [unclear] at once, and the construction of an apparaturs with refractory matter is a necessary condition of success. Rlubago [?] and clay well mixed together, and perhaps better still carbon under strong pressure, will be far preferable to metal because they will neither expand or contract as metal does. ### My present situation in reference to my Echophone is this. I have made here an anstrument in brass and saw that metal would not do. I have spent on the idea in experiments of diverse kinds, over one thousand dollars in America and over 600 here. To have a perfect instrument made with all requisites I require about 6 or 700 dollars, owing to moulds, patterns to be made, and tests of materials, and work by the hour with French woodmen working as many hours as they possibly can. They don't care here about completing a job in the least possible time; they consider on the contrary that having but one just they must make it last as long as possible and get as much as they possibly can out of it. Should you consider it possible to form a company or syndicate to supply me with the required amount to make an aparatus? The first one once made I feel pretty certain the instrument could be made for 15 or 20 dollars. ### You know that such an instrument is sure to bring profit. Edison's phonograph furnishes sufficient proof of it. But the range of my Echophone is much wider than the phonograph. I can lodge in it the singing of operatic actors as well as dramatic ones, and send the voices of the least singers all over the world to the millions who cannot come to them. In evening parties you will hear parts of an opera as sung in Paris or London and with the real voice of the great singers. And I repeat that my Echophone will render the sounds it will receive as powerfully as they are sung on the stage and they will be heard all over a room by all the persons present at the same time. I know that I can speak safely on this subject on account of what I have obtained from my apparatus made here, but I have to recourse to metal which will make the first instrument more costly. ### I have wirrten to America about my forme apparatus which will be sent to you after consulation with you. ### I wish to divide the profits by half with you or any company that may be formed to work out the patnet to be taken. Please let me know your views about it." Pleas ebelieve me, Dear Sir, Truly yours, Chs. Dion "Of course this is a confidential letter and I want you to say nothing to any one about the information I am supplying to you. I know that I can trust you, but I would not speak so freely with many people..."
Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University