Working of a Telegraph - Physics

TELEGRAPH

It is the first modern instrument used in sending messages to a distant place in a very short time. The working of telegraph is made efficient on using Morse code in which each letter is given a code of dots and lines. Important parts of telegraph system are electro magnet (M),battery (B), Morse key (K), and long wire called cable.
Different parts of the telegraph are connected at the place (A).
The Morse Key (K) is connected to positive terminal of battery (B), and the negative terminal is connected to ground (Earth).
From the Morse Key the cable runs to the place B. At the place B the cable is connected to electro magnet (M)and ground (Earth). An armature is held in the position, in contact with rod K, with the help of springs (S).

When the Morse Key K is pressed, the circuit is completed through ground which is a conductor. The electro magnet attracts the armature A and it produces a sound 'click' on striking the rod K2. On releasing the Morse key K, the circuit breaks and the armature goes to its original position touching the rod Kl.

If the time of contact of K is more it is called a line and if it is very short it is called dot.
Every letter like A,B,C,D and so on is allotted a code of dots and lines.
With the help of the code the message is transmitted at A and decoded at the station B to receive the message.