| Magneto generator: |
| When a wire passes through a magnetic field a current is induced in the wire. This principle is used for the generation of current in the telephone to ring the bell or actuate a shutter at the far end of a telephone installation. The armature of the generator is rotated by the handle and has its speed increased through gears to give the necessary voltage and frequency. Typical figures are about 70 volts and roughly 16Hz. |
| Note: To ensure that the magneto is only connected to the line when ringing out a cam "A","B" (Fig.171) causes the shaft to slide in the bearings to activate a set of contacts that connect the magneto to the line. |