Patent classifications
H
ELECTRICITY
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H04
ELECTRIC COMMUNICATION TECHNIQUE
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H04R
LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
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2499/00
Aspects covered by H04R or H04S not otherwise provided for in their subgroups
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