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.