History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 97
Fig. 38. the long arm, which is at the left in the cut. This lever isthrown up by a spring, so as to avoid contact with the button onthe frame below, except when the lever is depressed for the pur-pose of completing the circuit. A regulating screw is seen at … Fig. 39. the extremity of the short arm of the lever (Fig. 39) whichgraduates precisely the amount of motion of which it is at anytime capable. We are thus able, by resting with the finger upon the ivoryknob, to close or break the circuit at pleasure; if the contact THE MORSE SYSTEM. 79 between the…
Telegraph
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