Elementary telegraphy : a manual for students; written specially to meet the requirements of the ordinary grade of the subject as published in the syllabus of the city and guilds of London Institute (1910)
Pendry, H. W. (Henry Walter) · London ; New York : Whittaker & Co. · leaf 95
Fig. 04.—P.O. diileieiitial galvanometer TELEGRAPH INSTRUMENTS 85 Galvanometers. The P.O. pattern of differential galvanometer is illus-trated in Fig. 64. Tlie needle is either of the Varley orSpagnoletti induced types previously described, althoughin the former the bar magnets are placed below the…
Telegraph
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