Granted Patent
Utility
US 4,292,476 · App. 06/083,897
Speech channel switching networks suitable for use in combination with electronic key telephone sets
Inventors:
Kazuyuki Yamamoto, Seiei Ohkoshi
Patented Case
View Patent ↗
Granted: Sep 29, 1981
Filed: Oct 11, 1979
Inventors
Kazuyuki Yamamoto
Seiei Ohkoshi
Assignee (at issue)
Nippon Telegraph and Telephone Public Corporation
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.