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
Flo. 63.—Polaiiztd double suiiiider. G 2 Bi ELEMENTARY TELEGRAPHY
Telegraph
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