Granted Patent
Utility
US 4,669,110 · App. 06/791,263
Call progress tone system
Inventors:
Hedayat E. Daie, Charles H. Marsh, Joe L. Turner
Patented Case
View Patent ↗
Granted: May 26, 1987
Filed: Oct 25, 1985
Inventors
Hedayat E. Daie
Charles H. Marsh
Joe L. Turner
Assignee (at issue)
ITT 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.