Gongs or chimes, that strike only once when the button is pushed, are made by connecting the armature with the screw by means of a flexible wire.
A Special Kind of Electricity
Most buzzers and bells work on a much lower voltage than you normally find in the wires in your house. Some are made to work at 6 volts, others at 10 volts, and still others at slightly higher voltages.
You can get these low voltages by using one or more batteries, or by using a transformer connected to your house current. Most bells and buzzers are now powered through transformers.
How to Control Them
The push button is the most common means of control. You can use one button to control several bells, or several buttons to control one bell, or have several buttons control several bells. Because low voltage is used, adding extra buttons is simple, inexpensive, and safe.
Buzzers and bells can also be controlled by: clocks, as in the interval timer on an electric range or in a school class bell system; temperature detectors, as in a fire alarm or freezer alarm; door and window trips, as in a one-man repair shop or in a burglar alarm; and treadles, as in the driveway of a service station.
Figure 2