the bell to ring as long as the circuit from thebattery is closed : this is done by pushing the button, D. Electric Telegraph. — The electric telegraph has for manyyears been the principal means of rapid communicationbetween widely separated points. It consists essentially oftwo electro-magnets… … Fig. 116. Electro-Dynamics. H5 are so arranged that an electric current may be sent a longdistance and produce signals by which information of anykind may be given or received. The sending operatorcontrols the current by the key. This consists of a plati-num contact point so mounted on a lever that…
Physics
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