File:Bell telephone magazine (1922) (14733159376).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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aclosely controlled copper-zinc compo-sition, next to the rubber, good adhe-sion was secured not only when thewire was new but during service.However, it would not have been satis-factory to deposit the brass directlyon the bronze conductor, due to theresulting diffusion of the zinc into thebronze. To overcome this difficulty,and at the same time to afford cor-rosion protection, a coating of leadalloy was placed over the bronze con-ductor before the brass coating wasapplied. During this same period, the bronzeconductor itself received developmentattention. A new bronze was evolved,containing a larger amount of tinthan the older bronze. This bronzewas stronger, permitted the size of theconductor to be reduced, and at thesame time met the electrical conduc-tivity requirements for drop wire. 1 HE cotton braid covering of dropwire is needed to protect the wirefrom abrasion, and from sunlight,which would tend to cause crackingof the rubber. To improve its dura- 19^1 Evolution by Design 139
Text Appearing After Image:
Steps in the Development of Input TRANSFORArERs They form part of the repeaters used to amplify the currents at reifularly spaced intervals. along telephone toll lines. At the left is the transformer associated with an early type of repeater. The widely used transformer in the center has been superseded recently by the smaller one at the right, which requires less space and is improved electrically bility and increase the abrasion re-sistance, the braid is treated withweatherproofing compound. Many ofthese compounds have been studied.The present treatment involves satu-rating the braid with a mixture of se-lected asphalts and waxes, followedby a coating of stearine pitch and,finally, by a coating of ground mica.The decrease in conductor diameterhas made it practicable to use aheavier cotton braid and a correspond-ingly greater amount of weatherproof-ing compound than in the older wire,thus further increasing durability andabrasion resistance and at the sametime retaining the former cr

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