Granted Patent
Utility
US 5,535,271 · App. 08/250,783
Apparatus and method for dual tone multifrequency signal detection
Inventors:
Shrirang Jangi, Jie Chen
Patented Case
View Patent ↗
Granted: Jul 9, 1996
Filed: May 27, 1994
Inventors
Shrirang Jangi
Jie Chen
Assignee (at issue)
HUGHES ELECTRONICS LIMITED
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.