UTTONS.--Fig. 59 shows a
simple circuiting system which has two push buttons, although any number
may be used, so that the bell will ring when the circuit is closed by
either button.

THE PUSH BUTTONS AND THE ANNUNCIATOR BELLS.--Fig. 60 shows three push
buttons and an annunciator for each button. These three circuits are
indicated by A, B and C, so that when either button makes contact, a
complete circuit is formed through the corresponding annunciator.

[Illustration: _Fig. 60._ _Annunciators_]

[Illustration: _Fig. 61._ WIRING SYSTEM FOR A HOUSE]

WIRING UP A HOUSE.--The system of wiring up a house so that all doors
and windows will be connected to form a burglar alarm outfit, is shown
in Fig. 61. It will be understood that, in practice, the bell is mounted
on or at the annunciator, and that, for convenience, the annunciator
box has also a receptacle for the battery. The circuiting is shown
diagramatically, as it is called, so as fully to explain how the lines
are run. Two windows and a door are connected up with an annunciator
having three drops, or numbers 1, 2, 3. The circuit runs from one pole
of the battery to the bell and then to one post of the annunciator. From
the other post a wire runs to one terminal of the switch at the door or
window. The other switch terminal has a wire running to the other pole
of the battery.

A, B, C represent the circuit wires from the terminals of the window and
door switches, to the annunciators.

It is entirely immaterial which side of the battery is connected up with
the bell.

From the foregoing it will readily be understood how to connect up any
ordinary apparatus, remembering that in all cases the magnet must be
brought into the electric circuit.

CHAPTER VIII

ACCUMULATORS. STORAGE OR SECONDARY BATTERIES

STORING UP ELECTRICITY.--In the foregoing chapters we have seen that,
originally, electricity was confined in a bottle, called the Leyden jar,
from which it was wholly discharged at a single impulse, as soon as it
was connected up by external means. Later the primary battery and the
dynamo were invented to generate a constant current, and after these
came the second form of storing electricity, called the storage or
secondary battery, and later still recognized as accumulators.

THE ACCUMULATOR.--The term _accumulator_ is, strictly speaking, the more
nearly correct, as electricity is, in reality, "_stored_" in an
accumulator. But when an accumulator is