File:The Bell System technical journal (1922) (14755857555).jpg

Identifier: bellvol36systemtechni00amerrich (find matches)
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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a bottom pressures, is in-deed exposed to these pressures for the life of the repeater, but is notexposed to sea water. It is likewise a lead-through for electrical connec-tion from the cable to the glass seal. The core sleeve seal is an elastic barrier betw^een sea water on the out-side and a fluid on the inside. This fluid, polyisobutylene, is a viscoushoney-like substance, chemically inert, electrically a good insulator, anda moderately good water vapor barrier. It fills the long thin annularspace outside the cable core and inside a copper core tube and thusbecomes the medium of transmitting to the rubber seal the sea pressureexerted on the core sleeve. It can be seen that the core sleeve seal hasnominally no pressure resisting function and no electrical function. The same fluid is also used to fill the space between the glass and rub-ber seals. Voids at any point in the s^^stem of seals are potential hazardsto long, trouble-free life. Empty pockets, for instance, lying between the
Text Appearing After Image:
7i 73 o o 92 FLEXIBLE REPEATER DESIGN 93 central conductor and the outer conductor, or container, are capable ofbecoming electrically conducting paths if filled with water vapor. Aspointed out in companion papers,^ ^ the voltage between the repeater(and cable) central and outer conductors is in the neighborhood of 2,000volts at the ends of the transatlantic system. The filling of the seal interspace with a liquid would defeat one func-tion of the rubber seal if special features were not provided in the rubberseal design. Very slight displacement of the rubber seal toward the glassseal because of sea pressure, or resulting from reduction in volume owingto falling temperature, would otherwise build up pressure in the liquidand on the glass seal. We avoid this by providing a kind of resihence inthe interspace chamber. Three small brass bellows, partly compressed,occupy fixed cavities in the chamber. They can compress readily andmaintain essentially constant conditions independent of exte

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