Granted Patent
Utility
US 4,475,193 · App. 06/431,400
Power line carrier multi telephone extension system for full duplex conferencing between telephones
Inventor:
William M. Brown
Patented Case
View Patent ↗
Granted: Oct 2, 1984
Filed: Sep 30, 1982
Inventor
William M. Brown
Assignee (at issue)
ASTECH. CO., LTD.
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.