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Image from page 149 of "The Bell System technical journal" (1922) | by Internet Archive Book Images
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Image from page 149 of "The Bell System technical journal" (1922)

Identifier: bellsystemtechni16amerrich

Title: The Bell System technical journal

Year: 1922 (1920s)

Authors: American Telephone and Telegraph Company

Subjects: Telecommunication Electric engineering Communication Electronics Science Technology

Publisher: [Short Hills, N.J., etc., American Telephone and Telegraph Co.]

Contributing Library: Prelinger Library

Digitizing Sponsor: Internet Archive



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from about 20,000 miles per second, as on loaded cable circuits,to a speed approaching that of light. In developing a new toll system, there are many other factors, ofcourse, that must be considered. In our case, just as in yours, there 126 BELL SYSTEM TECHNICAL JOURNAL is first, an existiiiii toll telepluMio jilant, which imist be utilized to themaxitmnn ad\;uita.s;e. Also, distances between toll offices or tollcenters \ar\-, and particularh- the number of circuits required betweengiven [oW centers varies ovcv a wide range. It follows, therefore,that there is no one type of construction or method which can beeconomically utilized in all situations. Figure 5. for example, showinga poW line carrying open-wire circuits ami circuits in cable, illustratessome oi our present methods. The high-freiiuency broad-band tiansmission dexelopment is beingproposed foi three uses: (H for applicatiiMi on telephone toll cablesalreadx in cxistcme. or on future toll cables of \er>- similar t>pe of


Text Appearing After Image:

Fig. 5—A t\ polo lino carr\ ins; both opon wire and cablo. consnuciion: {2^ tor an extension to higher frequencies on open-wiretelephone circuits, sit as to secure more telephone channels on agiven pair; (^v^i for applicatii>n to new t\-pes of conductors capable oftransmitting a \-er> wide frequency band, such as the coaxialciMiductor. nmv being tried experimentally. 1 need hardly point out to you that as the frequency of transmissionis raised, the attenuation or line loss is greatly increased. This is duemore particulaiK- to two factors: an increase in series resistance dueto skin ettect. and an increase in shunt conductance due to increaseddielectric losses. As the frequenc>- increases, the currents transmittedtend moie and nune to a\oid tlie inner paits of the conductor and lo TOLL TRANSMLSSION IN TIIK UNITED STATES 127 concentrate on ihe surface, so increasing the effective series resistance.Dielectric losses in the insulalion between the conduclors also increas



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