Brechner, Claude H., 1887- [from old catalog] · Boston, New York [etc.] Allyn and Bacon · leaf 179
Figure 165. — Photograph of theTelegraph Relay. … Figure 166. — Photograph of a Telegraph Key. the key, relay, battery, and ground at Cleveland, returningthrough the ground to Chicago. Off each relay is run a local circuit, in which are a battery
Physics
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