Digital call progress tone detection method with programmable di

Details Digital call progress tone detection method with programmable di Digital call progress tone detection method with programmable di

1994-02-22

1996-10-08

Hofsass, Jeffery

Telephonic communications

Supervisory or control line signaling

Signalling integrity protection

379372, 379386, H04M 322

Patent

active

055639429

ABSTRACT:
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.

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"A Digital Receiver for Tone Detection Applications", Claasen et al., IEEE Transections or Communications, vol. Com-24, No. 12, pp. 1291-1300, Dec. 1976.

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