Ringer Of A Phone Bell

Operating Principle

The ringer works electromechanically. Basically it consists of two coils (wounded wire), which create a magnetic circle together with the lever of the clapper. When the coils are connected to an AC (alternating) voltage an alternating magnetic field arises which sways the lever and thus the clapper.

In order to ring a phone bell needs an AC voltage of 60 V with frequency of 25 Hz and with power of some Watts. In the early days this AC voltage was generated electromechanically by rotary inductors. These were driven by hand (phone crank) or by an engine (at the telephone exchange).

Usage Today

If you want to use such a ringer within a device today you must generate the 60V/25Hz AC voltage electronically. The AC voltage must be controllable and it must have enough power to drive the ringer. One way to do that is by means of a tree step procedure.

Generating the 60V/25Hz AC voltage in three steps:
1. Sine Generator (generates a sine wave with the right frequency but little voltage, e.g. 3 V, 25 Hz)
2. Power Amplifier (amplifies the sine wave to get enough power)
3. Transformer (transforms the small AC voltage to the final 60 V)