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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up of a smallglass tube from which is spurted a jet of acidulated water undera steady pressure capable of regulation. The glass tube isconnected to the diaphragm of the transmitter with an elasticenvelope and the jet of water falls between two platinum platesor sheets also capable of adjustment. With a steady jet there is a constant resistance between theplatinum plates, but if the diaphragm is made to vibrate thejet is correspondingly affected and the resistance between theplates is found to vary to a considerable extent and in exact 538 PRACTICAL TELEPHONE HANDBOOK accordance. As a strong current can be sent through, the plateswith no liability to heating, it will be seen that we have allthe requirements for a powerful form of transmitter with whichto vary, in one way or other, the high-frequency alternationssent into the aerial. A distance of 500 kilometres is said tohave been wirelessly spoken over with this transmitter. In operation the aerial is tuned so as to be resonant to the
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Fig. 490.—Fessendens Trough Carbon Transmitter period of the alternator, and acts with regard to the ethericwaves in a somewhat analogous manner to that in which a barof steel fixed at one end and struck at the other gives rise tosound waves in the air, or is even more analogous to the airvibrations in a closed organ pipe. If the vibrations are suffi-ciently rapid in such a pipe, musical sound waves are sentthrough the air, the effect being much enhanced if a resonantbox or tube is used in connection with the vibrating body ; so WIRELESS TELEPHONY 539 in the case of the aerial conductor, if the electrical vibrations oralternations are sufficiently rapid, electro-magnetic waves aresent through space from the aerial at the speed of light, or186,000 miles per second. By speaking into the transmitter while the alternator is inoperation, the resistance is caused to vary, the voltage of thesurging impulses in the aerial is by this varied in accordancewith the sound waves and the etheric w

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