21 BROADCAST TRANSMITTERS, CONDENSER MICROPHONES, OUTSIDE PICK-UP EQUIPMENT, SPEECH INPUT PANELS AND EQUIPMENT, BROADCAST STUDIO AND CONTROL ROOM APPARATUS, TRANSMITTING VACUUM TUBES, TRANSMITTING RECTIFYING TUBES,[CONDENSERS,]AIRCRAFT TRANSMITTERS, AIRCRAFT RECEIVERS, RADIO BEACON RECEIVERS FOR AIRCRAFT, GROUND STATION TRANSMITTERS, POINT-TO-POINT TELEGRAPH EQUIPMENT, RADIO BEACON TRANSMITTERS, PHOTOELECTRIC CELLS, WATER-COOLED VACUUM TUBES, AND RECTIFYING TUBES