Twentieth century manual of railway and commercial telegraphy (1905)
Meyer, Frederic Louis, b. 1875 · Chicago, New York, Rand, McNally & Company · leaf 16
In Fig. 1 we have a students Sset, that is,key and sounder on one board. It is connectedwith what is known as the gravity battery.The instrument has two posts from whichwires run to the battery. One wire runs to thezinc where it is connected with athumb-screw, the other runs tothe copper which is… … 14 THE TWENTIETH CENTURY
Telegraph
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