File:A system of multiplex telephony by the use of vacuum tubes (1919) (14773049625).jpg

Identifier: systemofmultiple00arno (find matches)
Title: A system of multiplex telephony by the use of vacuum tubes
Year: 1919 (1910s)
Authors: Arnold, E. H Throop, A. R
Subjects:
Publisher:
Contributing Library: Paul V. Galvin Library, Illinois Institute of Technology
Digitizing Sponsor: CARLI: Consortium of Academic and Research Libraries in Illinois

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
he radio frequency is beyond the audible limit, the two cir-CTiits shown inay function without interference. The modulation of a hi,Ph frecuenoy current isaccomplished by varying the amplitude of the wavebut not its frequency. ■?i?T.2 serves to illustratethe idea. The upper figure represents the oscil-logram of a voice current in an ordinary telephonecircuit, i^uch a current has a frequency of from 500to 2,000 cycles per second. The difference in mag-nitude of the succeeding waves is due to the vary-ing resist-^nce of the transmitter under the actionof sound ^aves. The middle figure sho^^s a high fre-quency current of constant amplitude and havingabove 20,000 cycles per second. The lower figurerepresents the audio frequency superposed upon theradio or high freouency. It is seen that the fre-quency is not changed, but merely the amplitudes. In the experiment as here described, the alt-ernator was run a^ such a speed as would producecurrent at a frequency of 100,000 cycles per second.
Text Appearing After Image:
10 ihe inductances and capaciHes were those ordina-rily employed in radio work. Using the circuitshown in iifr,. I, the inventor claims that absolutelyno interference was noticeable and that two con -versations were carried on simultaneously. The purpose of our work is to repeat these re-sults, and to develoD a combination receivinj^ andtransmitting circuit, which m.ay then be duplicatedat various frequencies to accomplish m.ultiplex tel-ephony. High frequency is to be generated by meansof electron tubes, and the receiving circuit is alsoto function by virtue of the characteristics ofthis apparatus. In its I9I8 report to the stockholders, theAmerican Teleo^r^ph and Telephone Company announcedthe success of a multiplex system in which five con-versations are carried on simultaneously. Thedetails of this system and the circuits used areentirely unknown to us at the time of this experiment-al investigation. II To beg-in the dipcussion of our work we willg-ive an outline of the operationsystemofmultiple00arno

Note About Images