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公开(公告)号：US2617222A
公开(公告)日：1952-11-11
申请号：US10361949
申请日：1949-07-08
Applicant: DAVID ROSENTHAL
Inventor： SAMUEL KATCHER
CPC classification number: G04B45/0092 , G09F3/18 , G09F7/02
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