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公开(公告)号：US1963254A
公开(公告)日：1934-06-19
申请号：US50711731
申请日：1931-01-07
Applicant: RADIO RES LAB INC
Inventor： URMSON WILLIAM G
IPC: H01J19/42
CPC classification number: H01J19/42 , H01J2893/0002
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