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公开(公告)号：US1762981A
公开(公告)日：1930-06-10
申请号：US28320028
申请日：1928-06-06
Applicant: BELL TELEPHONE LABOR INC
Inventor： HARTLEY RALPH V L
IPC: H04R19/02
CPC classification number: H04R19/02
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公开(公告)号：US1752486A
公开(公告)日：1930-04-01
申请号：US14514326
申请日：1926-10-30
Applicant: BELL TELEPHONE LABOR INC
Inventor： HARTLEY RALPH V L
IPC: H04R11/00
CPC classification number: H04R11/00
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