File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569826667).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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Fig. 518.—L. M. Ericssons C.B. System arranged for Measured Rate System current could be passed through the cell and the heat generatedbe rapidly dissipated. A later patent specification (No. 12,918 of 1909) describesmethods of stretching the diaphragms so as to ensure that thegreatest amplitude of vibration shall be at its centre, and alsoof so connecting subsidiary diaphragms for the granule cellsto the centre of the main diaphragm as to ensure a maximum 576 APPENDIX vibration in the microphone cell or cells. Fig. 519 showsone of the arrangements given, the fly nut on the top leftside being one of about 6 used to screw down a rimmededge of a round collar (shown only in section) on to aportion of the edge of the diaphragm which comes between thetwo edges of a recess in the circular frame. One of the micro-
Text Appearing After Image:
Fig. 519.—Egner and Holmstrom Transmitter(By permission of the Proprietors of Electrical Engineering) phone cells only is shown with a spring and screw arrange-ment for adjustment. For further particulars see ElectricalEngineering for 7th October 1909, also The Electrician, 19thNovember 1909. The Mercury-Arc Rectifier.—This is now used in several of theNational Telephone Co.s exchanges where the outside supply isalternating, and has given very good results. Its action depends on the fact that mercury vapour in a APPENDIX 577 vacuum tube at a certain pressure is a good conductor forcurrent in one direction but almost an insulator for current inthe reverse direction, so that if an alternating current be con-nected directly to the tube whilst an arc is maintained onlyone half of the I M -vVWWVWWV-7ron^, /~o r m e/~ -AA/WWW^ wave will be trans-mitted through thetube, the other halfbeing suppressed.By arranging amercury vapourtube in the mannershown in the cen- Qf\ «tre of Fig. 520 wi

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