Telegraph Key (Tapping Key), mounted on a solid plastic base, measuring 11 cm x 5 cm. Includes two contact screws/ knobs to simplify wire connection. Invention of telegraph and Morse code was the first step towards modern communication systems. All you need to make a telegraph station model is a tapping key, batteries and a simple electromagnetic sounder (clicker) that you can make at home. Making a telegraph circuit is a good way to learn more about electricity, electromagnet and digital communication.