Making A Two-Way Telegraph

Use a saw blade to make a key. If you can't find a short blade, ask an adult to wrap a cloth around a long saw blade and snap the blade in half.

Screw the key to one end of the wood, but do not tighten the screw yet. Put another screw in the other end of the board so that the key almost touches it.

Make a coil by winding a long piece of plastic-coated wire 50 times round a screw. Screw the coil into place on a piece of wood.

Insert a nail into a second piece of wood and nail the two pieces together with a third as shown in the picture.

Now fix the hinge in place supported by the nail. Leave a gap of about two millimetres between the hinge and the coil screw.

Make two keys and two sounders. Connect them to the batteries as in the picture. Now tighten the screws at the fixed end of the metal keys.

Test the system by pressing key 1 so that the free end of the metal blade touches the screw underneath it. This should make sounder 1 click. Test again with key 2 and sounder 2. If everything works, you are ready to start sending messages in Morse Code. Some help is given below in understanding Morse codes.

When you press a key, the current flowing through the wire coil makes the screw magnetic. It attracts the free arm of the hinge, which moves upwards and makes a click. When the key is released, the hinge falls back.