The practical telephone handbook and guide to the telephonic exchange (1906) (14775978803)

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

Text Appearing Before Image:

a current passing, the friction at the contact will be reducedin proportion to the strength of the current, and the discwill partly recover its position. On passing the undulatorycurrents from a transmitter through the contact, and con-tinuously rotating the cylinder, the disc will be caused tovibrate and give out a sound similar to that directed to thetransmitter. In order to moisten the chalk cylinder, it wasarranged that on depressing a handle, G, a small absorbent HISTORY 59 roller, R, was lifted out of a reservoir, t, containing the electro-lyte solution, and brought into contact with the chalk. When properly adjusted, the instrument was a powerfulone, giving out sounds that could be heard all over a largehall. The tone of the instrument, however, being verynasal, left much to be desired, and this, with the necessity ofmoistening the chalk and turning the handle, led to its dis-continuance. Wireless Telephone.—Many other interesting telephonic m^zzzzzzzzzzzgzzzgzzzzzzzzzzzzzzz

Text Appearing After Image:

Fig. 43 instruments have since been invented, such as the GrahamBell and Tainters Photophone (1879), in which advantageis taken of the fact that the resistance of some substances,especially a preparation of selenium, is affected by light.At the transmitting station a parallel ray of light is arrangedto fall on a polished vibrating diaphragm, from which thelight is reflected on to another reflector at the receivingstation, which concentrates the light on to the preparedselenium, the latter being included in a circuit containing abattery and a Bell telephone receiver. As the transmitting 6o PRACTICAL TELEPHONE HANDBOOK diaphragm vibrates, its polished surface curves, and so causesthe amount of light which falls on the selenium cell to cor-respondingly vary, and its resistance to vary proportionately,the sound being thus reproduced in the receiver. Fig. 44gives a sketch of the arrangement. In Tainters Radiophone the same effect is producedby heat-rays, these being absorbed by carbon in t

the practical telephone handbook and guide to the telephonic exchange 1906 book illustrations telephone bell telephone company transmitter radio images from internet archive

1906

Northeastern University, Snell Library

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public domain