Digital call progress tone detection method with programmable digital call progress tone detector

摘要

The present invention relates to a method of detecting call progress tones specified in a tone plan, comprised of calculating a power spectrum of a segment of an input signal containing a call progress tone, discriminating, based on the power spectrum, likely frequencies of the call progress tone, determining likely tone plan frequency bands based on between one and three of the frequencies, filtering the input signal in the frequency bands and extracting quadrature components of the input signal thereby, calculating three spectral moments of the input signal from the quadrature components for the frequency bands, and verifying at least one frequency of a call progress tone contained in the input signal based on the spectral moments.