Granted Patent
Utility
US 6,215,391 · App. 09/420,735
Variable frequency buzzer assembly
Inventors:
Matthew Murray, Ronald J. Johnsen
Patented Case
View Patent ↗
Granted: Apr 10, 2001
Filed: Oct 22, 1999
Inventors
Matthew Murray
Ronald J. Johnsen
Assignee (at issue)
ERICSSON GMBH
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.