File:The practical telephone handbook and guide to the telephonic exchange (1906) (14756093735).jpg

Identifier: practicaltelepho00pool (find matches)
Title: The practical telephone handbook and guide to the telephonic exchange
Year: 1906 (1900s)
Authors: Poole, Joseph
Subjects: Telephone
Publisher: New York, Macmillan Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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Text Appearing Before Image:
Fig. 82 So PRACTICAL TELEPHONE HANDBOOK of the particles of water. Wave motion in air is caused bya movement of the particles of air backward and forwardin a line with the direction in which the wave progresses.Every different sound needs a different motion of the airparticles for its conveyance, and if the characteristic motionof any sound can be impressed upon the air particles at anyplace, that sound will be reproduced. This was the problem attacked by Prof. Bell. BelVs Tele-rphonel the instrument with which Prof. Bell first succeeded,
Text Appearing After Image:
Fig. 33 is shown in Fig. 33, where e is an electro-magnet mounted soas to be adjustable near the centre of a membrane, m, of gold-beaters skin, stretched over the end of a hollow cylinder. Asmall piece of clock-spring is cemented to the centre of the mem-brane. Two of these instruments, some distance apart, werejoined in a circuit, including a battery, one being used as trans-mitter and the other as receiver. The action was as follows:—On speaking into the cylinder, the membrane moved in unisonwith the movements of the air particles. These movementsof the magnetic substance in front of the magnet producedalterations in the magnetic field in which the coils were situated.The effect was to cause electrical pulsations or waves to pass HISTORY 51 through the coils, the connecting wires, and the coils of thereceiving instrument at the distant end, of such a naturethat they so affected the attraction between the magnet andthe steel spring of the receiver as to set up exactly correspond-in

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