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公开(公告)号：US2240918A
公开(公告)日：1941-05-06
申请号：US21460838
申请日：1938-06-18
Applicant: RCA CORP
Inventor： ROELOF VERMEULEN , STEFANUS FUCHS HERMANUS
IPC: H04R9/12
CPC classification number: H04R9/12
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