Chapter 14

TELEGRAPH KEYS AND SOUNDERS.

APPARATUS 118.

_192. Telegraph Keys._ Fig. 92. Telegraph keys are merely pieces of apparatus by which the circuit can be conveniently and rapidly opened or closed at the will of the operator. An ordinary push-button may be used to turn off and on the current, but it is not so convenient as a "key." Fig. 92 shows a side view of a simple key. C is a metal strip about 3/4 in. wide and 4 or 5 in. long. At the left end it is fastened to the base with a screw, A. Another screw, X, serves as one binding-post. Y is another screw binding-post. W is a short wire, used to regulate the amount of spring to the key. This is done by moving W to the right or left. If the current enters at X, it will pass along C and out at Y, when C is pressed down. By moving C up and down according to a previously arranged set of signals, messages can be sent by means of the electric current. (See telegraph alphabet.) This apparatus is not a good one where the line is to be run with a "closed circuit battery," or where it is to be used very often. It will do, however, for places where a push-button would be too tiresome to use. The right end of C is curved. This curve serves as a handle. D and E are wires leading from X and Y.

APPARATUS 119.

_193. Telegraph Key._ Fig. 93. The base is 5 x 4 x 7/8 in. The key, C, is made of two thicknesses of tin. It is made into a strip 5-1/2 x 3/4 in., then the front end is bent up for a handle, as suggested in Fig. 92, the front end being above the base so that it will not touch the strap, D, unless it is pressed down. C is fastened to the base by a screw, H, which also binds one end of the copper wire, C W. About 3/4 in. from H is placed X, which is a screw-eye binding-post. Under C is the wire, W, which is used to regulate the amount of spring in C, by moving it forward or backward. S I shows the position of a screw-eye, or of an ordinary screw put into the base through C. The hole in C should be made so that C can move up and down easily around the screw. This is used to make a click when the key is allowed to spring up. The downward click is made when C strikes D at each depression.

The Strap, D, is made of tin. It is 4 x 1/2 in. before bending up the right end a little. It is fastened to the base by the screw, F, and by the other binding-post, Y. Its right end is raised enough to allow the arm, E, to pass under it, but it must press down well upon E when E is forced toward F.

The Swinging Arm or Switch, E, is also made of tin, and measures, finished, 4-1/2 x 1/2 in. Its front end should be bent up a little for convenience in handling it. (See Fig. 92.) E is pivoted at G by a screw, which also binds the wire, C W. Fig. 24 shows another way to make the pivot and connection.

194. Operation. See Fig. 99 for the details of the connections of a home-made telegraph line. When you are using the line and telegraphing to your friend, the switch, E, of your instrument must be open, as in Fig. 93, and the corresponding switch on his instrument must be closed; that is, the circuit must be opened and closed at but one place at a time. As soon as you have finished, your switch must be closed. He will open his and proceed. When you have both finished, both switches must be closed. If your friend left his switch open, you could not call him over the line, as no current could pass into his sounder.

195. Batteries. As the circuit has to be left closed for hours and perhaps days at a time, so that either operator can call the other, a closed-circuit battery is necessary. (See App. 9.) A dry cell, Leclanche, or other open-circuit cell would not be at all suitable for a telegraph line, as it would soon polarize. Large Daniel cells, which are 2-fluid cells like App. 7, or gravity cells (App. 9) are the best for your line.

APPARATUS 120.

_196. Telegraph Sounder._ Fig. 94. The wood-work consists of 2 parts; the base, B, is 6 x 4 x 3/4 in., and the back, A, is 6 x 5 x 1/2 in. A is nailed or screwed to B.

The Magnet, M, is fully described in App. 85. M is held firmly to A by cord or wire, which should pass around it near the poles and at the curved part. The wire should pass through small holes in A, and be tied at the back. Wire nails driven into A at the sides of M will keep it from moving about. The wires from the magnet coils are led to two spring binding-posts, X and Y.

197. The Armature, C, is made of a narrow piece of thin iron, about 5-1/2 x 1/4 x 1/8 in. It may be made by bending up 3 or 4 thicknesses of tin into that shape. This is the part which will be attracted by M, when the current passes, and which will make the clicks by which the message can be read. (See telegraph alphabet.) There are many ways by which C can be held near M. The figure shows how it can be done entirely with 1-in. wire nails. At the right end of C two nails are driven into A above and below C. They are just far enough apart to allow the left end of C to be raised and lowered without binding; in other words, these nails make a pivot for C to swing upon, and they help to support it at the same time. The left end of C must not quite touch the poles of M when the current passes, because the residual magnetism would keep C from dropping back into place. To adjust the armature, pass the current through M, hold C so that it will not quite touch the poles, then drive in the upper nail, 2. Put another nail, 1, below C, so that M will not have to lift C more than 1/8 or 3/16 in. Try the nails in different positions until C quickly rises and falls when the circuit is closed and opened. A nail, 3, driven in front of C, will keep its right end in place. No springs are needed, as gravity acts upon C instantly, bringing it to the lowest position as soon as the current ceases to flow.

198. The Battery will depend upon how much you want to use the sounder. 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.

The Key like App. 119 is best. Push-buttons 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 x 4-1/2 x 7/8 in. The back, A, is 7 x 4-1/2 x 1/2 in.; it is nailed to B. The piece D is 4 x 3/4 x 3/4 in.; it is nailed to A. C is a wooden piece 1-1/2 x 3/4 x 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 Sec. 125 and see Sec. 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.

APPARATUS 122.

_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 pass through easily. This acts as a bearing or pivot. L is kept up against V by the rubber-band, J, one end of which passes 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.

_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.

206. The Base, B, is 6 x 4 x 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 x 3/4 x 1/8 in., and made as described in App. 71. The piece, D, is 2-1/2 x 1-3/8 x 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 x 7/8 x 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 x 3/4 x 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 x 1/2 x 1/2 in., and is pivoted by means of N, which passes 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 unscrewing 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.

The Battery. It is supposed, if you make an instrument like this, that you expect to use it for a line. In that case make a regular gravity battery like the cell of App. 9. See Fig. 99 for line connections, and Fig. 98 for plan view of this sounder.

APPARATUS 124.

_209. Telegraph Line; Connections._ Fig. 99 shows the complete connections for our telegraph line, with two complete outfits. The capital letters are used on the right side, R, and small letters are on the left side, L. The batteries, B, b, are like App. 9. The keys, K, k, are like App. 119. The sounders, S, s, are like App. 121 or 122.

210. The two stations, R and L, may be near each other, or in different houses. The return wire, R W, passes from the copper of b to the zinc of B. This is important. If the cells are not joined properly, they will not work. It is better to have the cells together, on a short line, joined in series. The line wire, L W, and the return wire, R W, may be made of insulated copper wire for short lines in the house. Ordinary annunciator wire, No. 20, is good and cheap. The kind that is double cotton wrapped, waxed, and paraffined, has about 235 ft. to the pound. You should get at least 5 ft. for 1 cent. If your line stretches from one house to another you will find it better to use iron wire. Galvanized iron or steel wire No. 14 is good. This size weighs about 100 lbs. to the mile. The return and line wires must not touch each other at any point; they must not touch any pipe or other piece of metal that will short circuit your batteries. It is best to use porcelain or glass insulators to support your wires if the line is long; but for short lines, where you use a return wire, you may support the wires upon poles or trees by means of loops made of strong cord or wire.

211. Operation. Suppose R (right) and L (left) have a line. By studying Fig. 99 you will see that R's switch, E, is open while e is closed. The whole system, then, has but one place where the circuit is open. As soon as R presses his key, K, the circuit is closed, the current from both cells rushes around through K, S, L W, s, k, b, R W, and B. This magnetizes the bolts of both S and s, and their armatures come down with a click upon the regulating-screws, where they remain as long as the current passes. As soon as R raises his key the armatures rise, making the up-click. R can, in this way, regulate the time between the two clicks. If he presses K down and lets it up quickly, the two clicks that his friend L hears from s are close together; this makes what is called a dot. If R holds K down longer, it makes a longer time between the clicks for L to hear, and this makes a dash. R, of course, hears his own sounder, which is making the dots and dashes also.

As soon as R has finished, he closes his switch, E. L then opens his switch and proceeds to answer. Both E and e should be left closed when you are through talking.

(Read Sec. 194, 195, and study what is said in App. 9 about the gravity cell to be used on such a line.)

_212. Telegraph Alphabet._ The letters are represented by combinations of dots, dashes and spaces. A dot is made by pressing the key down, and raising it at once; that is, the key is raised as soon as it strikes. This makes the letter E. The dash is made by pressing down the key, and allowing the current to pass about as long as it takes to make 3 dots; this makes the letter T. A long dash for L should take about as long as for 5 dots. Spaces occur in a letter and between words. To make a dash you hesitate while the lever of the key is down, to make a space, you hesitate while the key is up. H is made with 4 dots without hesitation or space. By putting a space between the dots the letter &, Y or Z is made according to the position of the space. Notice that letters containing dashes do not contain spaces. A space is really the opposite of a dash. The letters C, E, H, I, O, P, R, S, Y, Z, and & are made entirely of dots or of dots and spaces.

You should notice that several letters are the reverse of others; A is the reverse of N, B of V, D of U, C of R, Q of X, and Z of &. The student should study some book upon telegraphy, if he desires to become expert. Punctuation marks are left out of the alphabet here given, as boys will find very little use for them.

A _ ___ B ___ _ _ _ C _ _ _ D ___ _ _ E _ F _ ___ _ G ___ ___ _ H _ _ _ _ I _ _ J ___ _ ___ _ K ___ _ ___ L ______ M ___ ___ N ___ _ O _ _ P _ _ _ _ _ Q _ _ ___ _ R _ _ _ S _ _ _ T ___ U _ _ ___ V _ _ _ ___ W _ ___ ___ X _ ___ _ _ Y _ _ _ _ Z _ _ _ _ & _ _ _ _

1 _ ___ ___ _ 2 _ _ ___ _ _ 3 _ _ _ ___ _ 4 _ _ _ _ ___ 5 ___ ___ ___ 6 _ _ _ _ _ _ 7 ___ ___ _ _ 8 ___ _ _ _ _ 9 ___ _ _ ___ 0 ______