The heart of the video camera is the vidicon tube which converts light entering the front lens to an electrical signal. An image is formed on a light-sensitive surface at the front of the tube. The image is then scanned by an electron beam, to give an output signal corresponding to the image brightness. The signal is recorded as a magnetic track traversing the tape diagonally. The sound track, which records the sounds picked up by the microphone, runs along the edge of the tape.