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公开(公告)号：US1919035A
公开(公告)日：1933-07-18
申请号：US54203231
申请日：1931-06-04
Applicant: BELL TELEPHONE LABOR INC
Inventor： PHELPS WALTER A , KOERNER ALLAN M
IPC: H04L25/08
CPC classification number: H04L25/085
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