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Telegraph engineering : a manual for practicing telegraph engineers and engineering students (1922)
Hausmann, Erich, 1886- · New York : D. Van Nostrand Company · leaf 154
Fig. 3. BU9Y TEST KNOBS .MAIN LINE fiENBRATOR ^RESISTANCELAMPTelegraph
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
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