File:A system of multiplex telephony by the use of vacuum tubes (1919) (14770693334).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
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Contributing Library: Paul V. Galvin Library, Illinois Institute of Technology
Digitizing Sponsor: CARLI: Consortium of Academic and Research Libraries in Illinois

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ch end of theline, in order to throw either a local battery tel-ephone circuit or a high frequency circuit on the 26 line. The ordinary telephone circuit was used totalk over when making changes and adjustments onthe circuits under test. Bepeater CircuitsThe first attempt at the use of vacuum tubesin wire telephony was for the purpose of relays ofspeech currents; and to this end we developed thecircuit sho^-m in fig.13. The transmitting circuitis shoTvn at the left usinp a VT_2 tube; and therecei^er circuit at the right using a VT_1. 4telephone transmitter T was connected in serieswith the primary of a telephone induction coil Lj;the secondary of this coil Lp being in the gridcircuit and balanced by the 2mf condenser Gj. Thegrid was kept at a potential of plus 10 volts. Inthis manner the grid potential is varied by thechange in potential at the terminals of the second-ary of the induction coil, which is due to thechange in priffiary current resulting from the actionof the transmitter.
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27 The plate circuit consists of a 2mf condenser Co andthe primary of a telephone induction coil L^. Ihesecondary, i^., of this coil is in the line as shown.From what has been said, it is evident that speechcurrents in circuit T,L);, Bj are repeated in an amp-lified condition in the line. ^he receiving end of the line contains the pri-mary of an induction coil L3 and a 2mf condenser,which, added to the line condensance balances roug-h-ly the line, he grid circuit of the VT-I tube iscoupled to the line thru the secondary of the induc-tion coil L^ and is balanced by condenser Cj. ^hereceiver plate circuit contains only a receiver inaddition to the 30 volt battery supplying potentialto the plate. The tubes were operated with normal operatingvalues and under the conditions outlined above. Or-dinary speech was amplified to such an extent thatthe words could be heard and understood at a dis-tance of three feet from the telephone receiver.Furthermore, speech was found to be very much morecle

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