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H04R21/021
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H
ELECTRICITY
H04
Electric communication
H04R
LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS DEAF-AID SETS PUBLIC ADDRESS SYSTEMS
H04R21/00
Variable-resistance transducers
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H04R21/021
with granular resistance material
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Patents Grants
last 30 patents
Information
Patent Grant
Microphone
Patent number
4,142,074
Issue date
Feb 27, 1979
The United States of America as represented by the Attorney General of the Un...
Charles K. Corbett
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3859478
Patent number
3,859,478
Issue date
Jan 7, 1975
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3845251
Patent number
3,845,251
Issue date
Oct 29, 1974
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3835266
Patent number
3,835,266
Issue date
Sep 10, 1974
C04 - CEMENTS CONCRETE ARTIFICIAL STONE CERAMICS REFRACTORIES
Information
Patent Grant
3825686
Patent number
3,825,686
Issue date
Jul 23, 1974
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3816108
Patent number
3,816,108
Issue date
Jun 11, 1974
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3437764
Patent number
3,437,764
Issue date
Apr 8, 1969
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3277247
Patent number
3,277,247
Issue date
Oct 4, 1966
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3103559
Patent number
3,103,559
Issue date
Sep 10, 1963
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
3064089
Patent number
3,064,089
Issue date
Nov 13, 1962
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2967914
Patent number
2,967,914
Issue date
Jan 10, 1961
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2960579
Patent number
2,960,579
Issue date
Nov 15, 1960
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2819351
Patent number
2,819,351
Issue date
Jan 7, 1958
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2748882
Patent number
2,748,882
Issue date
Jun 5, 1956
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2697136
Patent number
2,697,136
Issue date
Dec 14, 1954
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2609458
Patent number
2,609,458
Issue date
Sep 2, 1952
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2607859
Patent number
2,607,859
Issue date
Aug 19, 1952
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2583732
Patent number
2,583,732
Issue date
Jan 29, 1952
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2572525
Patent number
2,572,525
Issue date
Oct 23, 1951
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2567368
Patent number
2,567,368
Issue date
Sep 11, 1951
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2562526
Patent number
2,562,526
Issue date
Jul 31, 1951
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2539488
Patent number
2,539,488
Issue date
Jan 30, 1951
G01 - MEASURING TESTING
Information
Patent Grant
2538026
Patent number
2,538,026
Issue date
Jan 16, 1951
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2532694
Patent number
2,532,694
Issue date
Dec 5, 1950
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2532741
Patent number
2,532,741
Issue date
Dec 5, 1950
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2527159
Patent number
2,527,159
Issue date
Oct 24, 1950
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2521744
Patent number
2,521,744
Issue date
Sep 12, 1950
G01 - MEASURING TESTING
Information
Patent Grant
2494704
Patent number
2,494,704
Issue date
Jan 17, 1950
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2483317
Patent number
2,483,317
Issue date
Sep 27, 1949
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Information
Patent Grant
2435920
Patent number
2,435,920
Issue date
Feb 10, 1948
H04 - ELECTRIC COMMUNICATION TECHNIQUE
Patents Applications
last 30 patents