Image from page 873 of “The Bell System technical journal” (1922)

May 17th, 2016

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Image from page 873 of “The Bell System technical journal” (1922)
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Identifier: bell00systemvol31techniamerrich
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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Text Appearing Before Image:
siderations of economy and service improvement led to the intro-duction of carrier operation into all types of toll plant as rapidly as thestate of the art permitted. This directly affects the toll switching planfrom the standpoint of routing and location of switching centers. At present, carrier systems use four broad categories of facilities: openwire, conventional paired or quadded cables, coaxial cable and radio. Several types of open wire carrier systems permitting from one tofifteen telephone channels above the frequency band of the voice channelare now in use. In general these systems are used when> trunk cross-sec-tions are relatively small and where the terrain and weather conditionsmake open wire lines economical. Cable carrier systems at present permit the operation of up to twelvetelephone channels on two pairs of cable conductors. These conductorsmay be in one cable or divided between two separate cables, depending 84-4 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1952

Text Appearing After Image:
Fig. 10—Microwave radio relay tower at Cotoctin Mountain, Marj-land, on aNew York-Washington radio route. There are 300 message circuits in service withmore planned. on the type of carrier system (Fig. 8). Coaxial cable transmission systemscurrently provide up to 600 telephone channels per pair of coaxials(Fig. 9). A new coaxial system, under development, is expected to pro-duce about 1,800 telephone channels per pair of coaxials. Most of the applications of radio for toll telephone service now contem-plated, involve the use of pomt-to-pomt microwave systems. By employ- FUNDAMENTAL ILAXS FOK TOLL TKLKIMIONE PLANT 845 iiig rhaniioliiifz; (equipment at the tormiiiuls of these systems similar tothat used for the present coaxial system, eaeh pair of radio channels mayprovide up to (lOO telephone channels. Several pairs of such radio channelsmay be operated throuf>h the same antennas (Fi^- 10). Radio systems are also u.seful in some cases where the number of toiltriniks re(iuire(l is

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National Cherry Blossom Festival DC – April 12, 2014 by DJ Fusion (FuseBox Radio)
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National Cherry Blossom Festival DC – April 12, 2014 by DJ Fusion (FuseBox Radio)

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