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you to clamp them tightly by tightening on your screws E. Parts marked A are carbon and B the zinc pencil. The chemical solution consumes or oxidizes the zinc and the inactive element, the carbon stick collects the electricity. The zinc is the negative pole and the carbon is known as the positive pole. This simple battery if properly connected will ring electric bells, buzzers, etc.
Key and Sounder
A very simple telegraph key and sounder is shown in Figure 38. The base is made of 1/2-inch wood about 3 inches by
5 inches. Two sheet metal uprights are made, drilled and bent as at A, and a metal strip 1/2 inch wide and 2 inches long as at B. In the middle a small hole is drilled and a round head brass upholsterer tack is driven for the underside of the key to strike against to make a click. The bar C is made from a 3/8-inch by 3/8 inch piece of brass or iron, and a small hole drilled near the center for a small bolt to pass through in order to pivot it between the brass plates A. A hole drilled in the forward end will admit a brass screw that will hold a spool end to act as a finger-piece. This screw should be cut off and riveted at the underside. A short, strong spring is to be attached to the back of the base block and to the end of the key bar by means of a