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in the magnetic field set up a varying electrical current. The
current is carried along wires to the earphone of the person to
whom we are speaking.
The earphone contains a small electro-magnet and a
diaphragm similar to the one in the microphone. The varying
current is fed into the electro-magnet and causes it to exert a
varying attraction on the diaphragm, which vibrates and so
reproduces the sound that went into the microphone.
An electric bell is made to work by a “make-and-break”
circuit It consists of an electro-magnet whose armature is the
hammer of the bell. The circuit includes a pair of contracts, one of
which is attracted to the armature. A spring holds the armature in
such a position that the contacts are closed.
When the operating button is pushed, the electro-magnet
attracts the armature against the tension of the spring, and the
hammer strikes the bell. At the same time, the contacts are opened,
and so the circuit is broken and the spring returns the armature to
its former position. The contacts are now closed again and as long
as the button is pushed the armature will vibrate and the bell will
continue to ring.

Source: Adopted from “English for Technical Students” by
O.V. Buranova. Kyiv, 1994.

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