Granted Patent
Utility
US 6,178,241 · App. 08/870,892
Switch hook status determination in a communication system
Inventor:
Yan Zhou
Patented Case
View Patent ↗
Granted: Jan 23, 2001
Filed: Jun 6, 1997
Inventor
Yan Zhou
Assignee (at issue)
Legerity, 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.