Granted Patent
Utility
US 4,514,692 · App. 06/373,900
Metal detector and discriminator using differentiation for background signal suppression
Inventors:
David E. Johnson, Richard Williams
Patented Case
View Patent ↗
Granted: Apr 30, 1985
Filed: May 3, 1982
Inventors
David E. Johnson
Richard Williams
Assignee (at issue)
FRL, Inc.
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.