To make a model railway signal, you will need an iron nail, a straw, two pieces of plywood, a paper clip, a battery, a pencil and a length of copper wire. Fix the two pieces of plywood to each other.
They should be perpendicular to each other. Push the nail through the straw and fix the straw to the vertical ply board. Take a card and cut out a signal arm and fix it to the upper end of the jaw with the help of paper clip. Next take the pencil and wind some copper wire around it, making a hollow coil. There should be extra copper wire at both the ends. Place the coil on the horizontal plywood and connect it to the battery. Insert an iron nail inside the coil loosely. Taking another drawing pin and a paper clip, create a circuit. When you complete the circuit the nail will be attracted inwards into the coil. This is because it creates a magnetic field. You will find the signal arm move up and down lifting the signal.