American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 230
-quently happens in practice, c R is the condenser resistance, a s is a 3-point switchused in grounding the line, sc is a spark coil, or resistance box, adjusted toequal the internal resistance of the main battery. The other instruments are as marked,w. u. POLE-CHANGEK.—The Western Union standard… … W. U. POLE-CHANGER. through an aperture in the back of the framework. The tension springs s, s are in-sulated from the box. The contacts c c are attached to the framework. The poles ofthe battery are generally connected to the springs s s by way of their respectivebinding posts on the side of the…
Telegraph
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