Granted Patent
Utility
US 5,459,784 · App. 07/952,258
Dual-tone multifrequency (DTMF) signalling transparency for low-data-rate vocoders
Inventor:
Forrest F. Tzeng
Patented Case
View Patent ↗
Granted: Oct 17, 1995
Filed: Sep 28, 1992
Inventor
Forrest F. Tzeng
Assignee (at issue)
Comsat, 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.