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公开(公告)号：US1947749A
公开(公告)日：1934-02-20
申请号：US34415829
申请日：1929-03-05
Applicant: RCA CORP
Inventor： ROELOF VERMEULEN , YAN URK AREND THOMAS , CORNELIS LOMAN
IPC: H04R7/12
CPC classification number: H04R7/122
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