Granted Patent
Utility
US 4,220,828 · App. 06/001,813
Telephone subset
Inventor:
Hugo Ruzic
Patented Case
View Patent ↗
Granted: Sep 2, 1980
Filed: Jan 8, 1979
Inventor
Hugo Ruzic
Assignee (at issue)
International Standard Electric 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.