Title:
Directional acoustic system
United States Patent 2580439
US Patent References:
Bifocal distance sound concentrator
- - 2033337
Loud-speaking intercommunicating system
- - 2177769
Telephone system
- - 2224698
Sound amplifying apparatus
- - 2411004
Frequency selective apparatus
- - 2423459
Bifocal distance sound concentrator
- - 2033337
Loud-speaking intercommunicating system
- - 2177769
Telephone system
- - 2224698
Sound amplifying apparatus
- - 2411004
Frequency selective apparatus
- - 2423459
Inventors:
Kock, Winston E.
Publication Date:
01/01/1952
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Export Citation:
Assignee:
BELL TELEPHONE LABOR INC
Primary Class:
Other Classes:
181/144, 379/432, 367/176, 379/420.030, D14/243
International Classes:
H04R1/34; H04R1/32
US Patent References:
| 2483231 | Loud-speaking telephone set with low acoustic coupling |