Granted Patent
Utility
US 5,563,942 · App. 08/199,482
Digital call progress tone detection method with programmable digital call progress tone detector
Inventor:
Alexander F. Tulai
Patented Case
View Patent ↗
Granted: Oct 8, 1996
Filed: Feb 22, 1994
Inventor
Alexander F. Tulai
Assignee (at issue)
Mitel 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.