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Edison, His Life and Inventions [70]

By Root 7561 0
Hungary, was the first man to suggest a telephone exchange, and soon after exchanges were established. The telephone department was put in the hands of Hamilton McK. Twombly, Vanderbilt's ablest son-in-law, who made a success of it. The Bell company, of Boston, also started an exchange, and the fight was on, the Western Union pirating the Bell receiver, and the Boston company pirating the Western Union transmitter. About this time I wanted to be taken care of. I threw out hints of this desire. Then Mr. Orton sent for me. He had learned that inventors didn't do business by the regular process, and concluded he would close it right up. He asked me how much I wanted. I had made up my mind it was certainly worth $25,000, if it ever amounted to anything for central-station work, so that was the sum I had in mind to stick to and get--obstinately. Still it had been an easy job, and only required a few months, and I felt a little shaky and uncertain. So I asked him to make me an offer. He promptly said he would give me $100,000. `All right,' I said. `It is yours on one condition, and that is that you do not pay it all at once, but pay me at the rate of $6000 per year for seventeen years'--the life of the patent. He seemed only too pleased to do this, and it was closed. My ambition was about four times too large for my business capacity, and I knew that I would soon spend this money experimenting if I got it all at once, so I fixed it that I couldn't. I saved seventeen years of worry by this stroke."

Thus modestly is told the debut of Edison in the telephone art, to which with his carbon transmitter he gave the valuable principle of varying the resistance of the transmitting circuit with changes in the pressure, as well as the vital practice of using the induction coil as a means of increasing the effective length of the talking circuit. Without these, modern telephony would not and could not exist.[6] But Edison, in telephonic work, as in other directions, was remarkably fertile and prolific. His first inventions in the art, made in 1875-76, continue through many later years, including all kinds of carbon instruments --the water telephone, electrostatic telephone, condenser telephone, chemical telephone, various magneto telephones, inertia telephone, mercury telephone, voltaic pile telephone, musical transmitter, and the electromotograph. All were actually made and tested.


[6] Briefly stated, the essential difference between Bell's telephone and Edison's is this: With the former the sound vibrations impinge upon a steel diaphragm arranged adjacent to the pole of a bar electromagnet, whereby the diaphragm acts as an armature, and by its vibrations induces very weak electric impulses in the magnetic coil. These impulses, according to Bell's theory, correspond in form to the sound-waves, and passing over the line energize the magnet coil at the receiving end, and by varying the magnetism cause the receiving diaphragm to be similarly vibrated to reproduce the sounds. A single apparatus is therefore used at each end, performing the double function of transmitter and receiver. With Edison's telephone a closed circuit is used on which is constantly flowing a battery current, and included in that circuit is a pair of electrodes, one or both of which is of carbon. These electrodes are always in contact with a certain initial pressure, so that current will be always flowing over the circuit. One of the electrodes is connected with the diaphragm on which the sound-waves impinge, and the vibration of this diaphragm causes the pressure between the electrodes to be correspondingly varied, and thereby effects a variation in the current, resulting in the production of impulses which actuate the receiving magnet. In other words, with Bell's telephone the sound-waves themselves generate the electric impulses, which are hence extremely faint. With the Edison telephone, the sound-waves actuate an electric valve, so to speak, and permit variations in a current of any desired strength.

A second distinction between the two telephones is this:
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