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公开(公告)号：US2249131A
公开(公告)日：1941-07-15
申请号：US26267839
申请日：1939-03-18
Applicant: BELL TELEPHONE LABOR INC
Inventor： ERHARD HARTMANN , KREBS LUTHER E
IPC: H04R29/00
CPC classification number: H04R29/00
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