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; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
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1/00
Details of transducers,; loudspeakers or microphones
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H04R1/20
Arrangements for obtaining desired frequency or directional characteristics
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H04R1/22
for obtaining desired frequency characteristic only
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H04R1/222
for microphones
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