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公开(公告)号：US2426948A
公开(公告)日：1947-09-02
申请号：US57103345
申请日：1945-01-02
Applicant: RCA CORP
Inventor： JOHN PRESTON
IPC: H04R7/12
CPC classification number: H04R7/12
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公开(公告)号：US2234007A
公开(公告)日：1941-03-04
申请号：US14516837
申请日：1937-05-28
Applicant: RCA CORP
Inventor： OLSON HARRY F , JOHN PRESTON
IPC: H04R7/20
CPC classification number: H04R7/20
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