In some instances, the falling of the block might be made to complete a circuit through the magnet coils of a separate bell apparatus, instead of the magnet on the block being made to ring the bell.

From each room an insulated wire is led to the part of a building in which the apparatus is placed. In each room is, as usual, a contact apparatus by which such wire can be coupled to a main wire from one pole of a battery. The ends of all the wires are led Into the top of the casing of the apparatus. When the block is at the top of the case, a metallic contact mechanism carried by the block is in contact with each of the wires; the contact is also coupled to one end of the coils of the electro - magnet; this end of the coils of the magnet is also coupled to a metallic contact spring, which, when the block falls of metallic contact plates b, fixed at distances apart one below the other. There areas many contact plates as wires from the several rooms, and each plate is coupled to one wire. The other end of the coil of the magnet is coupled to another contact spring carried by the block, and this spring always rests against a metallic rod which extends from top to bottom of the case, and is coupled to the other pole of the battery.

In this way, whenever one of the wires leading from any room is, by the pushing in of a press - button or other contact apparatus, coupled up with the main wire from the battery, a current will pass through the coils of the magnet; the magnet will attract the armature attached to the catch, and will release the catch; the block will drop, passes over the contact plate, which is in connection with a branch of the same wire through which the current previously passed, the current again passes, the armature, which is then opposite to the poles of the magnet, is attracted, and the signal in connection with that armature is moved. The speed at which the block is allowed to descend can be controlled by suspending the block by a cord passed over a pulley, and having a counterbalance weight attached to it. The electro - magnet might be arranged.

Alternately the armatures may be made to travel in front of the fixed electro - magnet, and operated by a hanging weight. The successive completion of the different circuits will be made as specified, the relative movements of the magnet to the indicative armature and to the bell being the same. In the figure, c is the electro - magnet, fixed to a carrier or block d, which slides up and down the tube e. The block and magnet are suspended by the notched rod f, held by the lever detent g, which is provided with a soft iron armature, and is thus attracted to the magnet when the circuit is completed, releasing the magnet and block, and allowing them to fall; h represents any suitable galvanic battery, with different room circuits and bell pushes i. When the magnet reached the bottom of the case, spring k is in contact with the stud l, the termination of a permanently closed circuit. The recovered magnetism of the electro - magnet will then operate, by the vibration in the usual way of the spring armature m, an ordinary electric bell, which will continue to give warning until the attendant raises the electro - magnet to its former position, thereby also tilting back any displaced indicator label.

General Hints

(1) The amounts and sizes of silk - covered wire to be used for making coils for electric bells are as follows, the number of inches indicating the diameters of the respective gongs:- For a 2 - in. gong, 8 yd. of No.26; 2 1/2 - in., 9 yd. No. 26; 3 - in., 10 yd. No. 26; 3 1/2 - in., 10 yd. No. 26; 4 - in., 11 yd. No. 24; 5 - in., 12 yd. No. 22; 6 - in., 13 yd. No. 20. (2) The bells after being turned and polished receive an electro deposit of nickel or silver, or they may be warmed and lacquered with gold - lacquer in the lathe; screws and other brass fittings are done the same way. (3) It is immaterial whether the bell support be of iron or brass. (4) For winding the bobbins quickly and neatly, have a steel spindle, about 1/4 in. diameter, fixed in 2 bearings on uprights on a stand. Cut 2 pieces of stout brass tube (3/4 - in. common tube) each 1 in. long; turn each down taper to one end, and put a set - screw in each; then slide them over the 1/4 - in. spindle, so that their thin ends are nearest together.

Heels with holes of many different sizes can thus easily be fixed true and wound very easily, either in the lathe, or by hand by means of a small crank.

(5) A difficulty with the Leclanche battery is that the sal - ammoniac solution rises by capillarity, and attacks the leaden taps, brass binding - screws, and wires. The following suggestions relate to batteries: - (a) Take your battery to pieces, well wash in hot water to remove the chloride of lead, dry, and give a good coating of Brunswick - black; after setting up, give another, so as to thoroughly protect the leaden caps. (6) Try a few. drops of sweet - oil on the surface of solution, to prevent verdigris on binding - screws. Try a chloride of zinc battery instead of a Leclanche. A 4 - cell bichromate form battery, with sal - ammoniac solution, can be used for bells with great success and no trouble. (c) Avoid brass - work on Leclanche cells; prefer lead connections covered with Brunswick - black or black Japan varnish, which.prevents salts from creeping up and destroying the connections. Prefer wires (blacked over) to lead outside battery - box, having the terminals for connecting the cells outside the box.

A Leclanche set of 6 cells will work for nearly 3 years on a bell circuit by simply refilling with water occasionally. (d) Take out the carbons, well soak the heads in melted paraffin for say 2 in. down, then, by reheating carbons, drive back the paraffin for sufficient space for binding - screws to take on. If you have time, you might electrotype the heads and solder the binders to this. But in any case, you will find the paraffin wax prevent the creeping action of the excitant, (e) When you put the zinc rod into the solution (which should be only half up the outer jar), see that it is well amalgamated, and do not let it touch the porous cell. (/) To prevent the salt and water creeping up, grease the upper portions of the carbon, zinc, and jars; to check evaporation, place your cells in a wooden case, and screw on the front so as to be air - tight. When so fitted, if the insulation is good, Leclanche batteries of the best make will work well without any attention for several years; one working house - bells has been in daily use for 9 1/2 years, during which time it has been filled up with cold water 5 times, and been recharged once.