Granted Patent
Utility
US 4,563,652 · App. 06/722,774
Dual-stage filter with feedback
Inventor:
Bruce E. Hofer
Patented Case
View Patent ↗
Granted: Jan 7, 1986
Filed: Apr 12, 1985
Inventor
Bruce E. Hofer
Assignee (at issue)
AUDIO PRECISION, 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.