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公开(公告)号：US1809095A
公开(公告)日：1931-06-09
申请号：US23687527
申请日：1927-11-30
Applicant: BELL TELEPHONE LABOR INC
Inventor： WILSON JAMES R , BLACKBURN CHARLES M
IPC: H01J9/04
CPC classification number: H01J9/042
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