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Abstract

A process for determining the presence of either speech or one of a plurality of expected single-frequency signals on a line includes the steps of measuring the total signal energy on the line; measuring the signal energy present in each one of a plurality of selected separate frequency bands and identifying the two frequency bands having the highest signal energies; determining whether the highest signal energy exceeds a first selected threshold value; determining whether the highest signal energy exceeds the second highest signal energy by greater than a second selected threshold value; determining the amount of out-of-band signal energy; and determining whether the highest signal energy exceeds the out-of-band signal energy by greater than a third selected threshold value. A process for determining the presence of two of a plurality of expected a single-frequency signals on a line includes the steps of measuring the total signal energy on the line; measuring the signal energy present in each one of a plurality of selected separate frequency bands and identifying the three frequency bands having the highest signal energies; determining whether the two highest signal energies exceed a first selected threshold value; determining whether the second-highest energy exceeds the third-highest energy by a second selected threshold value; determining the amount of out-of-band signal energy and determining whether the sum of the two highest signal energies exceeds the out-of-band energy by a third selected threshold value; and determining whether the ratio of the two highest signal energy values exceeds a fourth selected threshold value. A method for identifying expected call progression signals on a telephone line, comprises the steps of (1) sensing the presence of energy on the line and determining if the energy comprises speech; (2) identifying the frequency content and duration of the energy; 3) comparing the frequency content of the energy with stored information comprising the frequency content of expected signals and identifying the energy as one of the expected call progression signals if a match is found; (4) sensing the presence of silence on the line if no match is found; (5) identifying the duration of the silence; (6) repeating steps (1) through (5) for a predetermined number of times; and then (7) comparing the frequency content of the energy, the duration of the energy, and the duration of the silence with stored information comprising the frequency content of energy, the duration of energy, and the duration of silence for a plurality of expected call progression signals and identifying the energy as one of the expected call progression signals if a match is found.

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First Claim