21 SOUND AND VISION EQUIPMENT-NAMELY, RECORDERS, REPRODUCERS, TRANSMITTERS, RECEIVERS, AMPLIFIERS; TELEPHONIC ELECTRIC ANNUNCIATORS AND CALL SYSTEMS FOR USE IN FACTORIES AND THE LIKE, PUBLIC ADDRESS SYSTEMS AND AUDITORIUM SPEAKERS, AMPLIFYING UNITS AND SPEAKER UNITS THEREFOR, AND PARTS THEREOF, PHONOGRAPHS, TUNERS, BOOSTERS, PICKUPS, SPEAKERS AND MICROPHONES