Patent ID: 7024357

Claim:
A method for detecting at least one tone having a known frequency and duration in an input signal, the input signal including a plurality of tones, the method comprising: a. determining at least an initial frame portion and a last frame portion of the at least one tone based at least partially on the frequency and duration of the at least one tone; b. determining an initial energy threshold detection level for the initial frame portion; c. determining an energy value indicative of the energy of the input signal for the initial frame portion; d. determining an energy threshold detection level for a subsequent frame portion based at least in part on the energy value of a previous frame portion; e. determining another energy value indicative of the energy of the input signal for a subsequent frame portion; f. comparing the energy values of the subsequent frame portion and a selected previous frame portion to determine if the at least one tone is present in the input signal; and g. repeating (d) through (f) for subsequent frame portions until the energy value for the last frame portion is compared to the energy value for a previous frame portion.