Bell telephone magazine (1922) (14754273564)

Identifier: belltelephonemag19amerrich (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

Text Appearing Before Image:

It was a two-way one-elementrepeater—a 21-type repeater, to usethe terminology later adopted. Camp-bell pointed out the advantages ofthe previously known but not used2 2-type repeater *; one in which twosimilar repeater circuits were used andtwo artificial lines. The lines whichentered a repeater station, in thatscheme, were not to be connected to-gether by a repeater circuit. Instead,each line was joined by a repeatercircuit to a dummy line; then thetransmitters of the two amplifyingelements were crisscrossed in connec-tion so that each element fed its out-going current to the line and the arti-ficial line which were associated withthe other repeater circuit. The Balancing Network Provesto be the Solution In this circuit it didnt make anydifference how unlike in impedancewere the two lengths of actual line;what was important was how closelyeach line was simulated in impedanceby the artificial line which balanced * Invented by W. L. Richards of the Ameri-can Bell Telephone Company.

Text Appearing After Image:

Vacuum Tube Repeater, 1914 This was the vacuum tube repeater ele-ment used in the test conversations betweenNew York and San Francisco it. If each of the lines on the twosides of a station were perfectly bal-anced by dummies (or networks),even though the two lines were of un-equal impedance, any current trans-mitted through the repeater in onedirection would divide with perfectequality between the line and its net-work, with the result that no currentcould flow back through the repeaterin the other direction. Of course,perfect balance is impossible; never-theless, this two-way two-element cir-cuit provided the margin necessaryto make transcontinental telephonypossible. The trouble was that aloaded artificial line would be bulky, 20 Bell Telephone Quarterly JANUARY very expensive to build, and twowould be required at each repeaterstation. Telling Hoyt his pessimistic con-viction, Mills stated his conclusionthat the only solution was to use the22-tj^e circuit, and he asked Hoytsopinion

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1922

Prelinger Library

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