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Scientific American, Vol. 42, No. 20 (1880) (1880)
leaf 4
fixed at its lower end. The sig- nal consists of a white disk with the word ‘‘ Answer” Fig. 7._ANNUNCIATORS, signal, the Ader visible signal, or the cail bell, as the sub- printed on it, and it may also bear the number of the corre- sponding subscriber.. This disk is attached to a pivoted scriber… … weighted or slightly flattened, or both, so.as being united in one group. Each switchman to cause the box to set upright. © 1880 SCIENTIFIC AMERICAN, INCInternet Archive · Public domain (published before 1931). Free to use for anything.
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