Patent ID: 6873701

Claim:
A system for determining a DTMF tone from an input signal, said system comprising: a trained data base for storing a plurality of reference templates, at least some of said reference templates representative of likelihood ratios; a likelihood ratio determination module coupled to said trained data base, said reference likelihood ratio determination module receiving a plurality of LPC coefficients, said LPC coefficients being representative of an input signal, said likelihood ratio determination module determining a plurality of current likelihood ratios based, at least in part, upon said LPC coefficients; a pattern matching module coupled to said trained data base and said likelihood ratio determination module, said pattern matching module determining an initial tone based, at least in part, on the minimum of said current likelihood ratios and the minimum of said reference likelihood ratios; and a tone acceptance module coupled to said pattern matching module, said tone acceptance module receiving a plurality of LSF coefficients, said LSF coefficients determined, at least in part, upon said input signal, said tone acceptance module verifying the validity of said initial tone based, at least in part, upon said LSF coefficients.