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Hearing aid transducer
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Patent number 4,867,267
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Issue date Sep 19, 1989
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Industrial Research Products, Inc.
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Elmer V. Carlson
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Passive ear protector
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Patent number 4,807,612
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Issue date Feb 28, 1989
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Industrial Research Products, Inc.
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Elmer V. Carlson
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A61 - MEDICAL OR VETERINARY SCIENCE HYGIENE
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Class D hearing aid amplifier
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Patent number 4,689,819
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Issue date Aug 25, 1987
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Industrial Research Products, Inc.
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Mead C. Killion
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Class D hearing aid amplifier
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Patent number 4,592,087
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Issue date May 27, 1986
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Industrial Research Products, Inc.
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Mead C. Killion
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Audio loudness control system
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Patent number 4,466,119
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Issue date Aug 14, 1984
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Industrial Research Products, Inc.
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Richard W. Peters
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H03 - BASIC ELECTRONIC CIRCUITRY
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Microphone with stepped response
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Patent number 4,450,930
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Issue date May 29, 1984
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Industrial Research Products, Inc.
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Mead C. Killion
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Priority mixer control
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Patent number 4,149,032
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Issue date Apr 10, 1979
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Industrial Research Products, Inc.
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Richard W. Peters
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Transducer coupling system
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Patent number 4,006,321
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Issue date Feb 1, 1977
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Industrial Research Products, Inc.
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Elmer V. Carlson
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Damping element
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Patent number 3,930,560
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Issue date Jan 6, 1976
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Industrial Research Products, Inc.
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Elmer V. Carlson
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G10 - MUSICAL INSTRUMENTS ACOUSTICS