The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 173
Scale I Fig. 164 switch-boards. The indicating part is a kind of white buttonor portion of a hollow sphere, a, attached to a pivot, B, andcounterbalanced by the curved soft-iron armature c, whichgradually widens from the point d. When the core e isenergised, c is attracted, moves round, and carries…
Telephone
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