The Drawdio was invented by Jay Silver and as the name suggests, you can use the Drawdio to draw while creating sound (audio).
The Drawdio circut is made from fifteen parts including a circuit board, capacitors, ceramic capacitors, resistors, transistors, a timer chip, a speaker, copper foil tape, a thumbtack, wire, and of course, a pencil.
The reason a pencil is used instead of a pen is because the graphite from the pencil is a conductor, there for electricity can pass through it enebling the Drawdio to function. How does it work? While writing with the Drawdio, the contact from the graphite and the paper completes a circuit that allows sound to be created and emitted through the speakers. Contact with your skin also acomplishes this. The reason being is that people are conductors of electricity and if you touch the end of the pencil's graphite or both sides of the pencil where the copper tape is placed, you are completing the circut which allows the electricity to flow through you body and make the pen work. It seems complicated but after putting it together, i've gained a better understanding of how it works.