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ELECTRICAL APPARATUS - NAMELY, LOUDSPEAKERS, EXPONENTIAL HORNS AND BAFFLES THEREFOR, MICROPHONES, AMPLIFIERS, PUBLIC ADDRESS SYSTEMS CONSISTING OF MICROPHONES, SPEAKERS, AMPLIFIERS AND INTERCONNECTING CIRCUITS THEREFOR AND PARTS FOR SUCH PUBLIC ADDRESS SYSTEMS, RADIO RECEIVERS, [ ELECTRIC PHONOGRAPHS, ] INTEROFFICE TELEPHONIC COMMUNICATION SYSTEMS INCLUDING MICROPHONES, SPEAKERS, AMPLIFIERS, TELEPHONE HANDSETS, AUTOMATIC SWITCHING EQUIPMENT AND INTERCONNECTING CIRCUITS THEREFOR AND PARTS FOR SUCH INTEROFFICE TELEPHONIC SYSTEMS, [ COMMUNICATION SYSTEMS FOR HOSPITALS, NURSING HOMES AND EXTENDED CARE FACILITIES COMPRISING ONE OR MORE NURSES CONSOLES, AMPLIFIERS, SPEAKERS, MICROPHONES, INDICATING MEANS, PATIENT CONTROL PANELS AND INTERCONNECTING WIRING FOR COMMUNICATION BETWEEN PATIENT AND NURSES; ] SOUND SYSTEMS FOR AUDITORIUMS, THEATERS, PUBLIC ADDRESS COMPRISING MICROPHONES, AMPLIFIERS, SPEAKERS, CONTROL CONSOLES, WIRING BETWEEN SPEAKERS AND OTHER PARTS OF SYSTEM FOR CONTROL OF QUALITY, VOLUME OF AUDIO-FREQUENCY ENERGY FROM SOURCES AS RADIO RECEIVERS, PHONOGRAPHS, LIVE TALENT; SCHOOL COMMUNICATION SYSTEMS COMPRISING MICROPHONES, SPEAKERS, AMPLIFIERS, CONTROL CONSOLES, AUDIBLE AND VISUAL ALARMS, RADIO RECEIVERS, [ PHONOGRAPHS, ] WIRING BETWEEN COMPONENTS TO PROVIDE SPEECH OR MUSIC, SIGNALS FOR CLASS ROOMS, MONITORING [ ; SECURITY SYSTEMS UTILIZING SONIC DETECTION COMPRISING SONIC GENERATORS, RECEIVERS, AMPLIFIERS, VISUAL AND AUDIBLE ALARMS AND PARTS THEREFOR AND CONNECTING WIRING ]