System and method for DTMF detection using likelihood ratios

Details System and method for DTMF detection using likelihood ratios System and method for DTMF detection using likelihood ratios

2005-03-29

2005-03-29

Isen, Forester W. (Department: 2644)

Telephonic communications

Supervisory or control line signaling

Signal receiver

C379S283000, C370S526000, C708S312000

Reexamination Certificate

active

06873701

ABSTRACT:
A system and method for determining DTMF coefficients stores a plurality of reference templates, at least some of said reference templates representative of likelihood ratios. A plurality of LPC coefficients is received. The LPC coefficients are representative of an input signal. The system and method determines a plurality of current likelihood ratios based, at least in part, upon the LPC coefficients. The system and method also determines an initial tone based, at least in part, on the minimum of the current likelihood ratios and the minimum of the reference likelihood ratios. A plurality of LSF coefficients is received. The LSF coefficients are determined, at least in part, upon the input signal. The system and method verifies the validity of the initial tone based, at least in part, upon the LSF coefficients.

REFERENCES:
patent: 4689760 (1987-08-01), Lee et al.
patent: 4853958 (1989-08-01), Rabipour et al.
patent: 5459784 (1995-10-01), Tzeng
patent: 5765125 (1998-06-01), Daugherty et al.
Gunter Schmer, “DTMF Tone Generation And Detection: An Implementation Using The TMS320C54x”, Texas Instruments, May 2000, pp. 1-19.

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