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 92
edlesecures a firm impact xii^onthe stop pins while the horse-shoe magnets retain theirmagnetism for a very long-period of time. The coils of the singleneedle have a resistance of200, and current required is15 to 20 m.a., although figureof merit is oOC) m.a. Twosounding pieces are now oftenfixed… … SiKignuletli iiulueeil iici- TllK DoUliLli .SOUXDEF!, This ccnnbination, hitherto termed the double platesounder, consists of a standard neutral relay (see p. (39)with two plate sounders in its local circuits, a S.C.galvanometer, and the sending part is a single needlecommutator. The two sounders…
Telegraph
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