. Bell telephone magazine . the mathematical papersof Oliver Heaviside, an English geniuswhose expositions were not always easy reading. What was needed wasa practicable engineering formulawhich could be applied to the con-struction of a telephone line. i HIS problem was attacked by morethan one engineer, and two arrived atsatisfactory solutions. One wasMichael I. Pupin, who, about 1900,showed that the desired effect couldbe obtained if the coils were insertedat certain regular intervals along theline. The other scientist who solvedthe problem was George A. Campbell,a member of the technical s
. Bell telephone magazine . the mathematical papersof Oliver Heaviside, an English geniuswhose expositions were not always easy reading. What was needed wasa practicable engineering formulawhich could be applied to the con-struction of a telephone line. i HIS problem was attacked by morethan one engineer, and two arrived atsatisfactory solutions. One wasMichael I. Pupin, who, about 1900,showed that the desired effect couldbe obtained if the coils were insertedat certain regular intervals along theline. The other scientist who solvedthe problem was George A. Campbell,a member of the technical staff of theAmerican Bell Telephone Companyin Boston. What these two men madeindependently was a basic inventionfor telephone lines, just as Bell hadearlier made the basic invention forthe terminal apparatus of which of them, however, belongedthe patent was only to be decided bya long court struggle, won by Pro-fessor Pupin, who sold rights to theAmerican Bell Telephone Company. Bell Telephone Quarterly JANUARY. acute form some years later when thehne was extended west from Denverpast Great Salt Lake. There, thewindblown salt spray had a seriouseffect on insulation, and considerablespecial engineering work and mainte-nance was required in that section ofthe transcontinental line. Mechanical Repeater, 1906Early Shreeve Type After this invention there remainedto be solved many problems in thedesign and construction of loadingcoils, many researches to be con-ducted, and further invention. Inthis continuing work the practicalformulae of Dr. Campbell provedmost important. When properly de-signed loading coils were spaced ap-proximately eight miles apart alongan open-wire telephone line, its trans-mission efficiency was just aboutdoubled. The effect of attenuationwas halved and there was possible thesame grade of telephonic transmissionas in a non-loaded line half as was about as much gain as couldwell be expected from loading, butit made telephony possible over
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