Piezo-electric acoustic device
United States Patent 1873715
Inventors:
Alexander, Meissner
Publication Date:
08/23/1932
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Assignee:
TELEFUNKEN GMBH
Primary Class:
Other Classes:
381/190, 367/163, 310/334, 310/328
International Classes:
G10K11/24; H04R17/00; G10K11/00