Granted Patent
Utility
US 4,987,402 · App. 07/423,987
Alarm system for sensing and vocally warning of an unauthorized approach towards a protected object or zone
Inventor:
Michael Nykerk
Patented Case
View Patent ↗
Granted: Jan 22, 1991
Filed: Oct 11, 1989
Inventor
Michael Nykerk
Assignee (at issue)
Electronic Security Products of California, 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.