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:
Sep. 06, 2005
Filed:
Feb. 21, 2002
Applicants:
Julian Lee, Vancouver, CA;
Gary Louie, Vancouver, CA;
Inventors:
Julian Lee, Vancouver, CA;
Gary Louie, Vancouver, CA;
Assignee:
VTech Telecommunications, Ltd., Tai Po, HK;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04M003/22 ;
U.S. Cl.
CPC ...
Abstract
A method and apparatus for detecting a signaling tone within a communications channel, such as a telephone line, is presented. The energy level of the communications channel signal is measured at the frequency of the signaling tone and at one or more frequencies that are integer divisors of the signaling tone (i.e. at one or more subharmonics). The subharmonic energies are evaluated in determining whether the signaling tone is present. The technique can be implemented using a plurality of resonators and a comparator.