Simple Methods of Connecting Call Bells
Wiring Diagrams for a Single Bell (Fig. 1, Fig. 2, Fig. 3)
The following diagrams will indicate a few of the various methods that may be employed in connecting up electric bells for different purposes, A, B and C representing the push buttons; D, the bells; E, the batteries, and G, the ground. The simplest possible connection is shown in Fig. 1, the bell D, battery E, and push button A, are all connected in series. The operation of the bell is independent of the order in which the bell, battery, and push button are placed, so long as there is a complete circuit when the push button is pressed. One of the wires in this circuit may be done away with by completing the circuit through the ground, as shown in Fig. 2. Connecting a bell as shown in this diagram often results in quite a saving of wire. The proper connections for operating one bell from either of two push buttons, A or B, is shown in Fig. 3. Two bells, D, operated from a single push button, C, are connected as shown in Fig. 4. The two bells, D, are shown connected in parallel, which requires more wire than if they were connected in series. If they be connected in series, one or the other should have its make-and-break contact closed. The bell whose circuit remains unchanged will intercept the current for the other bell in series with it. The operating of the bells is more satisfactory, however, when they are in parallel, and each taking current from the battery independent of the other.
Wiring Diagram for Two or More Bells (Fig. 4, Fig. 5, Fig. 6)
The diagram, Fig. 5, shows the proper connections for operating two bells from two independent push buttons, each push button operating a particular bell. Any number of bells operated from any number of push buttons, all of the bells being rung from any one of the push buttons, are connected as shown in Fig. 6. Such a circuit can be used as a fire alarm or time call in a factory, the operation of the circuit being controlled from any one of a number of different points.
Wiring Diagrams for Return-Call Bells (Fig. 7, Fig. 8, Fig. 9)
The proper connections for what is called a return-call circuit is shown in Fig. 7. The circuit is so arranged that the bell at one end is controlled by the push button at the other end. Such a circuit can be used in transmitting signals in either direction. A ground return-call circuit is shown in Fig. 8. In the circuits shown in Figs. 7 and 8, only one battery is needed.
The connections of a two-wire metallic return-call circuit are shown in Fig. 9. A special push button must be used in this circuit, and in this case two batteries are used instead of one, as in Figs. 7 and 8. This circuit may be changed to a ground return-call circuit by using the earth as a conductor instead of either wire. There are, of course, numerous other methods that may be used in connecting call bells, but the connections shown in the diagrams are perhaps the most common.