The elements of natural philosophy : copiously illustrated by familiar experiments and containing descriptions of instruments, with directions for using : designed for the use of schools and academies (1856)
Sprague, A. W. (Alfred White), 1821-1891 · Boston : Phillips, Sampson & Company · leaf 271
orbetween two trains. In this way an alarm may be given to or from a train inmotion at any point on the road. t Experienced operators of this as well as Morses machines often dispensewith the paper altogether, writing the messages directly out from the sound ofthe clicks upon the plate or cylinder.… … 237. The Signal-key or Break-piece, Fig. 216, is the instrument usually em-ployed for interruptingthe current and regulat-ing the system of linesand dots. This is placednear the battery, so as tobe in the galvanic circuit.One ^yire from the bat-tery entering the screw-cup, P, while the other…
Physics
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