File:Bell telephone magazine (1922) (14569514478).jpg

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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a short time after the inven-tion of the telephone in 1876, it be-came clear that the interconnection oftelephones in individual cities wouldbe the initial step in the developmentof this new device, but for maximumusefulness it would also be necessaryto interconnect the telephones in dif-ferent cities. The first long distancetelephone line was a grounded cop-per circuit about two miles in lengthbetween the Walworth ManufacturingCompany in Boston and their worksin Cambridge. It consisted of copperwire suspended by glass insulators.Up to about 1900, the early long dis-tance telephone circuits in the UnitedStates were practically all of this typeof construction, although it had soonbeen found that for the longer circuitsthe ground return at first used wouldnot give satisfactory results. By theuse of metallic (i.e., two-wire insteadof grounded) copper circuits, consid-erable distances were covered and by1884 a New York-Boston circuit hadbeen established. The open wire lines, however, soon
Text Appearing After Image:
^ -o \-, o i9^ii Trends in Toll Cable Usage 99 became inadequate to carry all thetoll circuits required and were subjectto damage from heavy ice conditionswhich frequently broke either thewires or the supporting poles andcrossarms. Before the turn of thecentury, the management of the BellSystem had come to appreciate theneed for improving the reliability ofthe more important toll circuits be-tween the larger cities, and there wascontinuous experimentation directedtoward finding some way to removethe toll circuits from open-wire typeof construction and put them in cable,where a lead sheath protects the cir-cuits from direct action of ice andother hazards. With cable, moreover,it is readily practicable to protect thecircuits further by placing them un-derground whenever this seems desir-able and economical. The problemappeared to be almost insurmount-able, as the transmission losses wereso large that with the types of cablesavailable a few miles of cable trans-mission was equivalent to

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