Granted Patent
Utility
US 4,837,642 · App. 07/143,911
Threshold tracking system
Inventor:
Peter Smidth
Patented Case
View Patent ↗
Granted: Jun 6, 1989
Filed: Jan 12, 1988
Inventor
Peter Smidth
Assignee (at issue)
Ampex 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.