Granted Patent
Utility
US 4,491,699 · App. 06/254,428
Communication apparatus for hostile environments
Inventor:
Martin Walker
Patented Case
View Patent ↗
Granted: Jan 1, 1985
Filed: Apr 15, 1981
Inventor
Martin Walker
Assignee (at issue)
NL Industries, 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.