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1.发明授权Telecommunication system employing voice frequency current for selective signaling 失效电话系统采用语音电流进行选择性信令
公开(公告)号：US2423084A
公开(公告)日：1947-07-01
申请号：US48627443
申请日：1943-05-08
Applicant: INT STANDARD ELECTRIC CORP
Inventor： DEN HERTOG MARTINUS , WRIGHT ESMOND P G
CPC classification number: H04Q1/444 , H04Q3/0016
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