Granted Patent
Utility
US 4,803,721 · App. 07/127,902
DC control circuit
Inventor:
Pierre J. Schingh
Patented Case
View Patent ↗
Granted: Feb 7, 1989
Filed: Dec 2, 1987
Inventor
Pierre J. Schingh
Assignee (at issue)
Mitel 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.