199. Telegraph Sounder. Fig. 95. This makes a simple and efficient sounder for short lines. The base, B, is 7 × 4½ × ⅞ in. The back, A, is 7 × 4½ × ½ in.; it is nailed to B. The piece D is 4 × ¾ × ¾ in.; it is nailed to A. C is a wooden piece 1½ × ¾ × ¾ in.; it is nailed to A, and in its top is a screw, E, which is used as a regulating-screw to keep the armature, L, from touching the poles.
200. The Armature, L, is explained as [App. 77]. The two thicknesses of tin at F must not be too thick, or it will take too much battery power to work the sounder. If you find that it is too stiff to bend down, when the current is on, try the arrangement of [App. 122], which is easier to make and regulate. The whole point depends upon the tin you have. The end of L must tap against E. A hole is punched in the part F, and a screw, G, holds it to D. L should rest about ⅛ in. above the poles and gently press against a screw or nail, V.
201. The Magnets are like [App. 89]. They are made as in [App. 88], and held down like [App. 90]. These should be placed very near the back, A, so that the armature will be over them. If your yoke is not too wide the coils may rest against A. Y and Z are binding-posts like [App. 46].
202. Connections. Join the coils as explained in [§ 125] and [see § 115]. Instead of a third or middle binding-post, as in Fig. 66, hold the two inside ends between a screw-head and a copper bur. The method of joining the wires for a line with two outfits, is shown in [App. 124]. If you have but one key, sounder, and battery, simply join the line wire to the return wire there shown. A gravity cell is best. ([See App. 9].)
203. Hints About Adjusting. If you have the right spring to the part F, of the armature, you will have no trouble. It must not be so weak that it allows L to strike upon the poles, as the residual magnetism (Text-book) will hold L down after the current has ceased to pass. No springs are necessary, if your tin is right. Do not have L too far away from the poles. The distance is regulated by the position of V. If you have trouble in getting it to work see [App. 122]. The poles must be opposite in nature.
