Part 13 (1/2)

If just to show the principle of it, almost any cell of medium strength will do, like that of App. 3, 4 or 5. A dry battery will do, but if you use the sounder much, an open-circuit battery will soon use itself up.

Where much work is needed of the battery use App. 9.

[Ill.u.s.tration: Fig. 95.]

The Key like App. 119 is best. Push-b.u.t.tons are handy where used only for experiments, and not for the actual sending of messages.

APPARATUS 121.

_199. Telegraph Sounder._ Fig. 95. This makes a simple and efficient sounder for short lines. The base, B, is 7 4-1/2 7/8 in. The back, A, is 7 4-1/2 1/2 in.; it is nailed to B. The piece D is 4 3/4 3/4 in.; it is nailed to A. C is a wooden piece 1-1/2 3/4 3/4 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 1/8 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 pa.s.s. 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.

APPARATUS 122.

[Ill.u.s.tration: Fig. 96.]

_204. Telegraph Sounder._ Fig. 96. The magnets, connections, etc., are like those of App. 121, no binding-posts, etc., being here shown. The armature is straight, however, the part F resting upon D. A hole is made in the end of F, and through this is a screw or nail, S. The hole must be large enough to allow S to pa.s.s through easily. This acts as a bearing or pivot. L is kept up against V by the rubber-band, J, one end of which pa.s.ses around the end of L; to the other end of J is a thread, which is tied around a screw-eye, K. By turning the screw-eye, the band may be made to pull more or less upon L. In this way the apparatus may be regulated according to your battery. The general dimensions and explanations are given in App. 121. D is made of such a height that it will bring L about 1/8 or 3/16 in. above the poles.

APPARATUS 123.

[Ill.u.s.tration: Fig. 97.]

_205. Telegraph Sounder._ Figs. 97 and 98. This apparatus looks a little more like a regular sounder than App. 121 and 122, but it is much harder to make and adjust. In this the lower nuts of the bolts are not sunk into the base, and the magnets are made of 2-in. bolts. If you change this and fasten them like App. 89 and 90, it will simply change the dimensions of the small parts. The sizes given are for this particular instrument.

Fig. 97 shows a perspective view, and Fig. 98 is a plan or top-view of it, with dimensions.

[Ill.u.s.tration: Fig. 98.]

206. The Base, B, is 6 4 7/8 in. The magnet, M, is explained in App.

89. Its wires are attached to the binding-posts like App. 46. The armature, A, is 2-1/2 3/4 1/8 in., and made as described in App. 71.

The piece, D, is 2-1/2 1-3/8 1/2 in., and is screwed to B from below, after the two uprights, C, are nailed to it. The uprights, C, are 2-3/4 7/8 1/2 in. They are nailed to D. The nail, N, runs through both uprights, and acts as the bearing for F to rock up and down upon.

The hole for N is 2 in. above B. It must not be too loose in the holes, or F will rock sidewise, and allow A to touch one of the magnets. The upright, E, is 2-3/4 3/4 3/4 in., and is screwed or nailed to B from below. A screw, G, is put into the side of E near the top. This screw has the underside of the head filed flat, and against this the screw, L, taps when the armature is attracted. The arm, F, which carries the armature, A, is 4-1/2 1/2 1/2 in., and is pivoted by means of N, which pa.s.ses through it and the uprights C. F must swing up and down freely. The hole for N, in this model, is 1-3/4 in. from the armature end.

207. The armature is fastened to F by a screw, S. A copper bur is put under the head of S to aid in keeping A from rocking sidewise. Through F, and about half way between C and L, is put a screw, I, the lower end of which taps against the head of a screw, H, which is put into D. By uns.c.r.e.w.i.n.g H a little, F will be raised, and A will be brought nearer the poles of M. The rubber-band, J, is placed over the head of I, and has tied to it a thread, O, which in turn is tied to a screw-eye, K. K screws into the end of B, and by turning it one way or the other, the tension, or pull, on J may be increased or diminished. There must be enough spring in J to pull A up after the current ceases; it must not pull so much that the magnet cannot draw A down hard enough to make a good click between L and G.

The Magnet, M, is explained in App. 89, and the construction of one bolt magnet is given in detail in App. 88. In this particular sounder the bolts are 2 in. long under the heads, thus bringing the tops of the bolt-heads about 2-1/4 in. above B. M is held to the base by a band of tin, T. The yoke may be screwed to B, as suggested in App. 90. This is the better plan.

208. Adjustment. You will find, although you make all of the parts with the dimensions given, that you will have to try, and change, and adjust before everything will work perfectly. A must not be allowed to touch the poles of M when it is pulled down, on account of the residual magnetism, which would keep it pulled down. Adjust this with F. The armature must not be pulled too far up from the poles of M by the tension in J; adjust this with I and H. If your battery is weak, the pull of J must be small, just enough to raise A.