History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 518
Fig. 106. patterns manufactured by Mr. Hall. A great variety of these instru-ments have been manufactured, and each manufacturer generallymakes several different patterns. Fig. 107 is a drawing of Mr. Phelpss latest pattern of the relaymagnet. Fig. 32 shows one made by the Messrs. Chester of… … Fig. 107. 42, 43 exhibit drawings of the olden pattern of sounders, now butlittle used.
Telegraph
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