Rigid circular plate of either metal or plastic used to record video and audio signals for playback. It resembles a phonograph record and can be played on a machine attached to a conventional television receiver. There are two major classes of videodiscs, magnetic and nonmagnetic. Magnetic videodiscs have an oxide-coated surface onto which input signals are recorded as magnetic patterns in spiral tracks. Nonmagnetic videodiscs use either a mechanical recording system analogous to that used in phonograph records, or optical technology that uses a laser to read data coded as a sequence of pits on the disc. The most common type of videodisc today is the DVD.