Granted Patent
Utility
US 4,621,354 · App. 06/685,197
DTMF receiver sense and control maintenance arrangement
Inventors:
Leo V. Jones, Jr., A. Lee Walsh
Patented Case
View Patent ↗
Granted: Nov 4, 1986
Filed: Dec 21, 1984
Inventors
Leo V. Jones, Jr.
A. Lee Walsh
Assignee (at issue)
GTE Communication Systems 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.