Granted Patent
Utility
US 5,267,312 · App. 07/764,557
Audio signal cryptographic system
Inventors:
John R. Thompson, C. J. Hunting, William L. Phipps, Steven J. Raynesford, Philip H. Rittmueller
Patented Case
View Patent ↗
Granted: Nov 30, 1993
Filed: Sep 20, 1991
Inventors
John R. Thompson
C. J. Hunting
William L. Phipps
Steven J. Raynesford
Philip H. Rittmueller
Assignee (at issue)
NEC Home Electronics, 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.