Granted Patent
Utility
US 6,415,139 · App. 09/198,379
Detection circuit of tone signal
Inventor:
Atsushi Shimbo
Patented Case
View Patent ↗
Granted: Jul 2, 2002
Filed: Nov 24, 1998
Inventor
Atsushi Shimbo
Assignee (at issue)
OKI ELECTRIC INDUSTRY CO., LTD.
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.