Patent search ap:("BELL TELEPHONE LABOR INC") AND inv:"ENTZ FERDINAND S" Page 2

11.

发明授权
Telephone system 失效

公开(公告)号：US1708983A

公开(公告)日：1929-04-16

申请号：US12968326

申请日：1926-08-17

Applicant: BELL TELEPHONE LABOR INC

Inventor： EDWARD VROOM , ENTZ FERDINAND S

IPC: H04M3/40

CPC classification number: H04M3/40

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