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, 2003
Filed:
Sep. 28, 1999
Todor Cooklev, Salt Lake City, UT (US);
Mark Gray, Salt Lake City, UT (US);
3Com Corporation, Santa Clara, CA (US);
Abstract
A method and system for facilitating the detection of DTMF tones is disclosed. The method is based on detecting two tones using a modified nonuniform discrete Fourier transform that includes a phase correction term for each DTMF tone and harmonic. The disclosed method is employed by a DTMF detector that includes a sampling module, a computation module, an analysis module, and a decode module. The sampling module samples an input signal from a communication network at a rate sufficient to avoid data loss. The sample signal is then placed through a modified DFT which is more precise than filters or analog devices, particularly those utilizing a Goertzel algorithm. The computation module implements a fast recursive algorithm for completing the necessary computations. The analysis module checks for the present of energy level peaks at the DTMF tones and their harmonics. Once a DTMF signal is verified to contain a DTMF tone, the decode module transmits the,number, letter, or symbol to an interface.