Identifier: belltvol20elephonemag00amerrich (find matches)
Title: Bell telephone magazine
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept
Subjects: Telephone
Publisher: (New York, American Telephone and Telegraph Co., etc.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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de-creasing the resistance along thesheath. The relationship between earth re-sistivity and the geological structureof the United States has been thesubject of considerable study by theBell System. From this study a verygood general knowledge of the earthresistivity which may be expected inany area has been obtained. Bymeans of these data on earth resistiv-ity, and information obtainable fromiso-ceraunic charts, which show thefrequency of thunder storms in allsections of the country, it is possibleto predict in a general way the rela-tive amount of trouble from lightningwhich might be experienced with bur-ied cable in any particular region. The engineering work on the trans-continental cable, accordingly, in-cluded a careful investigation of theroute from this standpoint, with thehelp of these charts and of accuratefield measurements of the earth re-sistivity at intervals along the route.Based on the data thus obtained, pro- i 9f 1 Engineering the Transcontinental Telephone Cable 219
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An Unattended Repeater StationThis structure at Durham, Wyo., is typical of those built at intervals on the cable route.They house the delicately attuned equipment required to amplify the currents as they becomeattenuated along the line. The apparatus is designed to operate for considerable periodswithout direct attention, control circuits to the nearest attended station indicating any need for testing or trouble clearance tective arrangements against lightningdamage were designed for the cable.These arrangements vary in the dif-ferent sections, but include such plansas increasing the insulation betweenthe core and the sheath by doublingthe thickness of the paper wrapping ofthe core, placing copper shield wiresin the same trench with the cables, oradding copper wires between thesheath and the core, and combinationsof these measures. For example, in asection east of Cheyenne, and fromCheyenne to Denver, shield wires areburied in the trench with the cables.Going west from Cheyenne the e

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