File:Bell telephone magazine (1922) (14569433008).jpg

Identifier: belltelephonemag4344amerrich (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

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
cause signal lossesor diminution over coaxial conductorschange with temperature, most coaxialcables are buried so they may assume thetemperature of the earth, which is rela-tively constant. The amplifiers which counteract suchattenuation are located every few milesin structures either above or belowground. In all modern coaxial transmis-sion systems, these amplifiers operate au-tomatically and are powered remotelyfrom attended stations usually located atcommunications terminals or intercon-necting points. Early Coaxial Cables A Philadelphia-New York coaxialcable, which was experimentally demon-strated in October, 1936, was the firstlong distance broadband transmissionsystem. The following year, in Novem-ber, a similar cable was used to transmittelevision between a local broadcastingstudio and the Empire State Building inNew York. Coaxial cable was introduced on a com-mercial basis in June, 1941, over the 195-mile distance between Minneapolis andStevens Point, Wisconsin. This cable had
Text Appearing After Image:
Transistorized terminal equipment is seen above; craftsman checks transmission levels of a group of hroadhand circuits. 22 four coaxial tubes—two for working pur-poses and two for protection—and its amplifiers were spaced at eight-mile in-tervals. This was the first use of the coaxial carrier system known as L-1,which was designed to provide 480 two-way telephone circuits in a pair of tubes.Later, circuitry was developed to obtain 120 additional circuits. The L-3 System To meet the rising demand for commu-nication services after World War II, a coaxial cable system of still greater ca-pacity was needed. After six years of development work in Bell Laboratories and more than a year of field trials, a carrier system (coded L-3) was achieved.With this system, one pair of coaxial tubes can furnish up to 1,860 telephone circuits. With L-3, amplifiers are spaced at shorter intervals—four, rather than eight miles. An L-3 system was placed in service in 1953 between New York and Philadel-phia. Since

Note About Images