The easiest way to contact a person is to pick up the phone, dial a number and you can have the conversation with that person even if the person is many miles away or anywhere on the earth. Nearly 100 years back you have to write a message or letter which reaches in days but now the whole scenario has changed. So how this small device works?

It converts the speech or sound energy to electrical energy which can be sent anywhere. All the telephone systems are connected and controlled by central offices or exchanges which give path for all the electric signals to travel.

The working of first telephone was almost similar to the today’s phone. The waves of sound coming out from the mouth are exactly copied by the transmitter. Carbon grains are present behind the transmitter so when the electric waves pass through them it gets vibrated according to the electric energy they are receiving and on the other side there is coiled wire having magnet within it attached to the diaphragm. Now according to the current the wire gets vibrated so as the diaphragm. So these vibrations move air and create sound on the other end.

Working of telephone is almost same as in past but only the microphones were as simple as carbon granules compressed between two thin metal plates other things are as it was in the past. A switch for the connection of network is called the hook and a speaker.

Your telephone is generated with the power of 48V in the exchanges but the old and ordinary offices use 400 ohm line relay coils in series with a line whereas in 48V there is 200 to 400 ohm series.

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