novel equipment utilizing a single head , single gap on a single track in an audio magnetic recorder to permit control of a large variety of audio - visual devices for the pre - programming of a multi - media presentation in educational , entertainment and other fields . particular structure , including an audio magnetic tape drive mechanism , which permits , by means of a single head with a single gap on a single track , index signal recording , data signal recording , data signal updating and data signal playback is provided to perform multiple discrete and proportional control functions . the same magnetic tape may carry on a separate track or tracks audio information which is correlated with the functions controlled by the data recorded on the device control track .