The cells commonly used for annunciators, bells, etc., are the “Laclede” and “Laclanche,” and are generally taken to have an E. M. F. of one and one-half volts; the “Danniell,” one volt; others vary from one to two volts when in good order.
To renew these cells fill the jar two-thirds full of clean water, add six ounces sal ammoniac, let it dissolve; then put in the zinc and carbon; be sure they are perfectly clean; and that the zinc is not worn out or eaten away. There are two ways to connect up these cells; the first is “in series” for E. M. F., the second “in parallel” for quantity. The first method “in series” is as shown. This way the E. M. F. is in proportion to the number of cells, three cells having three times the E. M. F. of one volt.
The second method, “in parallel” for quantity, is as shown; all the negatives (zinc) are connected, and all the positives (carbon) connected, making the current obtained of much greater volume, but only of the E. M. F. or intensity of one cell.
The strength of a current given by a battery varies with the resistance, as well as with the E. M. F., and can be increased not only by adding more cells “in series,” but also by lessening the internal resistance, viz., by increasing the size of battery plates, or more simply by coupling all the + (positive) poles together, and all the - (negative) poles together. The E. M. F. of cells coupled in this way is only equal to that of a single cell, but the current will be greater because the internal resistance will be only one-third that of a single cell. This plan is called coupling up for quantity, or “in parallel,” to distinguish it from the plan of “in series,” or for intensity.
The E. M. F. of a large and small cell are both the same (using same size elements). To increase E. M. F. multiply the cells “in series.”
The ordinary battery carbon is a mixture of carbon and peroxide of manganese—“Oh, Mr. Window Trimmer, please see if you can make this bell ring.” Bell No. 7 is dead, and there is no end of trouble; this is something met with occasionally. Examine the battery, see that it has not become crystallized (polarized), and if so, disconnect one cell at a time. Clean it well, without wetting the outside of jar, recharge with new zinc (if required) and six ounces powdered sal ammoniac, jar being first filled two-thirds full of warm water, or enough to avoid overflow; replace cell, connect up and take out another. Be sure to reconnect the cells left in battery, so as to keep it working while you are cleaning each one. A good way, if you don’t think the cells need changing, is to take a small call bell or buzzer, with short wires, disconnect both ends of battery, then test every cell by placing a wire on each pole of the cell at same time. If cell is all right, bell will ring. Suppose you find cells all right, proceed to bell No. 7, the dead one, examine the push button, and trace the wires from bell to battery, being sure they are not grounded by lying on some steam or gas pipe with the insulation worn off. (If it should be a case of continual ringing, the wires are crossed.) You may expect a “ground” if the battery has run down suddenly or too quick. If the trouble is found in the annunciator, don’t bother with it, unless you are expert or want trouble. Send for an electrician; it will save time—in other words, money.
SPECIAL WINDOW WIRING.
Many houses have ample facilities for electrical work, but as they do not employ a house electrician many beautiful and attractive effects are barred in their windows. Even when an attempt is made to introduce electrical effects into displays the results are tame and insignificant, because of a lack of special wiring. Yet we know that the success of many windows depends largely upon their illumination.