The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 05, 1982
Filed:
Apr. 07, 1980
Applicant:
Inventors:
Gary Grantland, Hartselle, AL (US);
Larry A Woodworth, Huntsville, AL (US);
Assignee:
GTE Automatic Electric Labs Inc., Northlake, IL (US);
Attorneys:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04M / ;
U.S. Cl.
CPC ...
179 / ; 179 / ;
Abstract
An improved loudspeaking substation circuit employing a dual-tone multi-frequency signal generator wherein output tone levels are regulated by the substation transmission circuit when operating in either a loudspeaker or handset mode. The circuit further provides for preventing acoustic feedback and self-oscillation between the loudspeaker and handset transmitter while transferring between either mode.