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 71
armatures. The large currents required for direct working sounders 60 ELEMENTAR Y TELEQBA PHY cannot be obtained in circuits of more than a few miles■\vitliout inconveniently increasing tlie battery power. Hitherto it has 1)een tlie practice when the line exceededabout 6 or 8 miles in length to… … FiG. 3-2.— Vyle polarized sounder. able signals with currents of one-tenth the vahie requiredfor the ordinary sounder. As will be seen from the illustration in Pig. 32, thepolarized sounder in appearance resembles the ordinaryinstrument. The soft iron yoke is replaced by a strong-horseshoe magnet…
Telegraph
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