Tunzelmann, George William von, 1856- · New York, Scribner & Welford · leaf 203
nnection with theline is made directly when the hookrises, instead of by the subsequentmotion of a lever. The exchange is provided with anI instrument called a switch-board,and it will be easier to understandthe process followed by consideringin the first place a switch-board of asomewhat simpler… … THE TELEPHONE EXCHANGE SYSTEM. 187 of his magneto, a current is sent through the hne and thecoils of a small electro-magnet placed at the back ofthe upper part of the board, immediately behind oneof the drop-shutters shown in the illustration. Theelectro-magnet, being excited by this current, lifts…
Electric industries · Electricity
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