Granted Patent
Utility
US 4,896,346 · App. 07/274,151
Password controlled switching system
Inventors:
William R. Belfield, William J. Erwin, Thomas J. Geers, Jr., Roy V. Grubbe, Stephen W. Handy, Robert J. Perdue
Patented Case
View Patent ↗
Granted: Jan 23, 1990
Filed: Nov 21, 1988
Inventors
William R. Belfield
William J. Erwin
Thomas J. Geers, Jr.
Roy V. Grubbe
Stephen W. Handy
Robert J. Perdue
Assignee (at issue)
American Telephone and Telegraph Company, AT&T Bell Laboratories
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.