Title:
Acoustic device
United States Patent 1762981


Inventors:
Hartley V, Ralph L.
Application Number:
US28320028A
Publication Date:
06/10/1930
Filing Date:
06/06/1928
Assignee:
BELL TELEPHONE LABOR INC
Primary Class:
Other Classes:
381/174, 381/191, 381/427
International Classes:
H04R19/02
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