PROGRAMMABLE DIGITAL CALL PROGRESS TONE DETECTOR

摘要

The present invention relates to a method ofdetecting call progress tones specified in a tone plan,comprised of calculating a power spectrum of a segmentof an input signal containing a call progress tone,discriminating, based on the power spectrum, likelyfrequencies of the call progress tone, determininglikely tone plan frequency bands based on between oneand three of the frequencies, filtering the input signalin the frequency bands and extracting quadraturecomponents of the input signal thereby, calculatingthree spectral moments of the input signal from thequadrature components for the frequency bands, andverifying at least one frequency of a call progress tonecontained in the input signal based on the spectralmoments.