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:
May. 06, 2008
Filed:
Oct. 17, 2003
Joachim Fouret, London, GB;
Masoud Ahmadi, Harlow, GB;
Mohamed El-hennawey, Belleville, CA;
Can Liao, Belleville, CA;
Joachim Fouret, London, GB;
Masoud Ahmadi, Harlow, GB;
Mohamed El-Hennawey, Belleville, CA;
Can Liao, Belleville, CA;
Nortel Networks Limited, St. Laurent, QC., CA;
Abstract
A fast DTMF detector for filtering a packetized linear voice signal to identify whether the voice signal contains a DTMF tone. The detector includes a plurality of parallel notch filters for knocking down DTMF tones. The energies of the filtered signals output by the notch filters are calculated and criteria based upon the calculated energies are applied to determine if the voice signal contains a DTMF tone. The criteria include an energy differential test, a twist test, a low frequency tolerance test, a high frequency tolerance test, a packetized linear voice signal energy level test, a dial tone filtered signal energy level test, and a 1004 Hz filtered signal energy level test.