Patent ID: 7933216

Claim:
A method of detecting whether a voice signal communicated over a digital voice network includes a modulated data signal, the method comprising: (a) determining a first time interval between a first phase reversal in the voice signal and a second, consecutive, phase reversal in the voice signal, by using an algorithm that searches for lowest autocorrelation value; (b) if the first time interval is within a predetermined range of time values, then determining that the voice signal includes a modulated data signal; (c) if the first time interval is not within the predetermined range of time values, then: (i) determining a second time interval between the second phase reversal in the voice signal and a third, consecutive, phase reversal in the voice signal, by using said algorithm that searches for lowest autocorrelation value; (ii) if the second time interval is within said predetermined range of time values, then determining that the voice signal includes a modulated data signal.