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 103
edin the tube and tlie opposition of the closely confined airl)()11i combine to make the mirror move eraduallv, and if 92 ELEMENT A R Y TELEGRA PHY the damping effect is considerable it will stop dead iu itsfinal position, returning to zero when the current ceases. A more delicate form of… … VAN£ s V. N DISC Fio. 72a.—Astatic form of Thornsgalvanometer needles.
Telegraph
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