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 87
Fig. 54.—3-terrainal ■2-\vav switch. … Fio. .55.—6-terminal Siniiilex Duplex switch. circuits it is termed the simplex diiplex switch, but itspositions are now marked 1 and 2 to adapt it for manyother purposes requiring a double two-way change. Theterminals occupying j)ositions corresponding to XII and YI TBLEGRA PU INHTH UMENfS 11 oil…
Telegraph
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