A rubber band or a small wire spring passing over a screw and connected at the other end to the armature will draw the latter away from the magnets when the current is not passing. The terminals of the magnets are connected to binding-posts mounted on the base. [Illustration: Fig. 134.—A Diagram showing how to connect two Simple Telegraph Stations.] The key and sounder should be placed in series with one or two cells of a battery. Pressing the key will then cause the armature of the sounder to be drawn down and make a click. When the key is released, the armature will be drawn up by the spring or rubber band and make a second click. Hardly a boy interested in mechanics and electricity has not at some time or other wished for a telegraph instrument with which to put up a "line" with his chum. A practical working set of such instruments can be very easily constructed, and with little expense, by following the sketches and instructions given here. The magnets for the sounder may either be constructed by the intending telegraph operator or secured from some old electrical instrument such as a magneto-bell. In the latter case, the hardest part of the work will be avoided. If they are to be home-made, the following suggestions may prove of value in carrying out their construction. [Illustration: Fig. 135.—A Complete Telegraph Set, consisting of a Keyboard and a Sounder.] The cores are made from one-quarter-inch stove-bolts with the heads cut off. The magnet heads are cut out of hard-wood fiber, one-eighth of an inch thick and one inch in diameter. They should fit tightly and be held in place with glue. They are separated so as to form a winding space between of seven-eighths of an inch. The magnets should be wound full of No. 25 B. & S. gauge cotton-covered wire. [Illustration: Fig. 136.—Details of the Telegraph Set shown in Figure 135.] The yoke is made of enough strips of sheet-iron, one-half inch wide and two inches long, to form a pile one-quarter of an inch thick. Two one-quarter-inch holes are bored in the opposite ends of the yoke, one and one-half inches apart. The lower ends of the magnet cores are passed through these holes. The ends should project one-half of an inch beyond the yoke. They are passed through two holes in a base-board three-quarters of an inch thick. The holes are countersunk from the lower side, so that a nut can be screwed on the lower end of each and the magnets held tightly in an upright position. The remaining parts of the instrument are very easily made, and are so clearly shown by the drawing that it is hardly necessary to say more than a few words in explanation. The lever or tongue, the anvil, the standard, and the lever of the key are all cut out of hard-wood according to the pattern shown in the illustration. The armature is a piece of soft iron fastened to the lever with a small brass screw. Tacks are placed under the heads of the adjusting screws on the sounder so that it will click more loudly.