Twinkle box

During the past fifteen years, use of two-dimensional computer input/output devices has become commonplace. Since the earliest uses of the light pen for target identification in air defense systems it has been obvious that two-dimensional input would be interesting and useful. A large number of two-dimensional tablets and digitizers have been developed and have come into quite effective use. These devices have made use of mechanical, electrical, magnetic, optical, and acoustic phenomena. (See bibliographical references.)