808 



THE TELEPHONOGRAPH. 



an arm mounted on the left side of the frame .strikes the tiny lever 

 shown in the illustration, raising the magnet, and causing it to run 

 rapidly back to the beginning again (the carrier being guided by the 

 coarse threaded shaft, shown parallel to the supporting shaft) this 

 operation taking but rive seconds. The legs of this magnet are about 

 seven-sixteenth inch long, and are wound with bobbins of wire of 

 about the same size as those employed on an ordinary receiving tele- 

 phone magnet. A cross section of the magnet is shown in fig. 2, let- 

 ter ('. It has been found that a horseshoe form of magnet, as shown 

 in fig. 2, letter B. will not respond rapidly enough, and it is preferable 

 to employ two separate magnets electrically connected, as shown in 

 fig. 2. letter C. In the ribbon form of telephonograph the horse- 

 shoe magnet shown in fig. 2, letter I>. may lie used, but even here 

 two magnets electrically connected are preferable. This recording 

 electro-magnet, which has a resistance of K>() ohms, is connected in 

 circuit with an ordinary carbon telephone transmitter, and a couple 

 of cells of battery, and preferably with an induction coil in the usual 

 manner. When the transmitter is spoken into, it acts as a tap upon 



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Telephonograph magnets. 



the battery and causes currents of varying strength, and in propor- 

 tion to the strength of the sound waves impinging upon the diaphragm, 

 to pass through the wire wound on the electro-magnet. Now as the 

 steel wire wound on the drum passes in front of and in contact with 

 the poles of the magnet, its varying magnetic field magnetizes trans- 

 versely the steel wire, and the "lines of force" are permanently 

 recorded therein. After the steel spiral has been filled, which opera- 

 tion takes about thirty-nine seconds at an ordinary speed of talk- 

 ing, and records 100 to 120 words, the tiny magnet is placed at the 

 point where the record first started, and in place of the transmitting 

 telephone with which it was connected a Bell receiving telephone is 

 attached. The cylinder or drum again revolves, and as the magnet- 

 ized steel wire passes before the poles of the electro-magnet it forms 

 a speciesof magneto-electric generator, giving out currents of electricity 

 of a strength and direction corresponding to the magnetization of the 

 steel wire, which correspondingly affect the Bell telephone, and repro- 

 duce the sounds and words originally spoken with absolute fidelity. In 

 Edison's phonograph and its modifications, such as the graphophone, 

 gramophone, etc.. a stylus is always employed to indent the surface of 



