. The practical telephone handbook and guide to the telephonic exchange . :V777ZZ&2Z^ Fig. 37 On the same day that Bell filed his patent, Prof. E. Gray 54 PRACTICAL TELEPHONE HANDBOOK also filed one with very similar suggestions for producing varia-tions in the resistance of an electric circuit. Edisons Carbon Transmitter.—Edison, in 1878, was the firstto produce a successful instrument based on the variation ofresistance principle. He took advantage of the fact discoveredby Du Moncel, that the increase of pressure between twoconductors in contact produces a diminution in their electricalresis
. The practical telephone handbook and guide to the telephonic exchange . :V777ZZ&2Z^ Fig. 37 On the same day that Bell filed his patent, Prof. E. Gray 54 PRACTICAL TELEPHONE HANDBOOK also filed one with very similar suggestions for producing varia-tions in the resistance of an electric circuit. Edisons Carbon Transmitter.—Edison, in 1878, was the firstto produce a successful instrument based on the variation ofresistance principle. He took advantage of the fact discoveredby Du Moncel, that the increase of pressure between twoconductors in contact produces a diminution in their electricalresistance. This is eminently the case with carbon, whichwas the substance chosen by Edison, its great variation ofresistance under pressure having been independently dis-covered by him. The instrumentEdison finallyadopted after manyforms had been ex-perimented with,was that known asthe button trans-mitter, shown inFig. 38. d is a micadiaphragm clampedto the iron case bythe iron cap, in which is screwed the ebonite mouthpiece against <,the centre of d is
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
