Part 3 (2/2)

[Ill.u.s.tration: Fig. 21.]

APPARATUS 34.

_50. Sifters_ may be made by p.r.i.c.king holes in an envelope. A sifter with very small holes can be made of a piece of muslin cloth. This can be used in the form of a little bag, or a piece of it can be pasted over the open bottom of a pill-box.

APPARATUS 35.

_51. To Cut Wires, Nails, etc._ If you have no wire-cutters, or large shears, you can cut large or small wires by hammering them against the sharp edge of another hammer, an anvil, or a piece of iron. Do not let the hammer itself hit upon the edge of the anvil. The above process will make a V-shaped dent on one side of even large wires, or nails, when they may be broken by bending back and forth.

CHAPTER IV.

SWITCHES AND CUT-OUTS.

_52. Switches, Cut-Outs._ Where apparatus is to be used frequently, such as for telephone and telegraph lines, it pays to make your switches, etc., carefully. The use of these switches, etc., will be shown in the proper place. Their construction only will be given here.

APPARATUS 36.

_53. Cut-Out._ Fig. 22. Details. X, Y, and Z represent 3 binding-posts like App. 42. These are fastened to a wooden base that is about 3 5 3/4. The ends of the wires shown come from and go to the other pieces of apparatus. Q shows a stout wire or strip of 2 or 3 thicknesses of tin.

Suppose we have an apparatus, as, for example, an electric bell, which we want to have ring when someone at a distance desires to call us. If we use a telephone or telegraph instrument we shall want to cut the bell out of the circuit as soon as we hear the call and are ready to talk.

Suppose the current comes to us through the wire, A, Fig. 22. It can pa.s.s by the wire, C, through the bell and back to X. If we wanted simply to have the bell ring, the current could pa.s.s directly from X into the earth, or over a return wire back to the push-b.u.t.ton at our friend's house. If, however, we are to use some other instrument, by lifting the end of Q out of X and pus.h.i.+ng it into Y, the bell will be cut out, and the current can pa.s.s on wherever we need it.

[Ill.u.s.tration: Fig. 22.]

APPARATUS 37.

_54. Cut-Out._ Fig. 23. The main features of this are like those of App.

36. The three binding-posts are like App. 46. Instead of a band of metal to change connections, as Q in App. 36, a stout copper wire is used.

This can be easily changed from one of the upper binding-posts to the other, thereby throwing in or cutting out any piece of apparatus joined with the upper connectors.

[Ill.u.s.tration: Fig. 23.]

APPARATUS 38.

[Ill.u.s.tration: Fig. 24.]

_55. Switch._ Fig. 24. This simple switch has but one contact point, D, which is a screw-head. This switch may be used anywhere in the circuit by simply cutting the wire carrying the current, and joining the ends of the wire to the binding-posts X and Y. The metal strip, E, is made of 2 or 3 thicknesses of tin. It is 5/8 in. wide and about 5 in. long, and presses down upon D, when swung to the left, thus closing the circuit.

The short metal strips shown are 5/8 1-1/4 in. The upper strip is joined to the end of E by a coiled copper wire, C W. (See App. 50.) If the current enters by the wire, A, it will pa.s.s through C W, E, D and out at B. The strip E is pivoted at F by a small screw. The base may be 3 or 4 5 7/8 in.

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