Granted Patent
Utility
US 4,347,409 · App. 06/178,950
Key telephone system
Inventors:
Seiki Ogawa, Michio Mito, Tsuyoshi Shinoi
Patented Case
View Patent ↗
Granted: Aug 31, 1982
Filed: Aug 18, 1980
Inventors
Seiki Ogawa
Michio Mito
Tsuyoshi Shinoi
Assignees (at issue)
Nippon Telegraph and Telephone Public Corporation
Nippon Tsushin Kogyo Kabushiki Kaisha
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.