Patent ID: 6587559
Filing Date: 2003-07-01
Classification: H04M

Abstract:
A signal detector, comprising:a transform unit adapted to receive at least a first and a second frame of time domain input samples, generate at least a first frequency energy value for the first frame, a second frequency energy value for the second frame, a third frequency energy value for the first frame, and a fourth frequency energy value for the second frame based on the time domain input samples, wherein the first and second frequency energy values are associated with a first tone frequency, and the third and fourth frequency energy values are associated with a second tone frequency; and a cross-frame energy level unit adapted to compare the first frequency energy value to the second frequency energy value to determine the presence of a first tone in the time domain input samples and compare the third frequency energy value to the fourth frequency energy value to determine the presence of a second tone in the time domain input samples, and the cross-frame energy level unit is adapted to determine a first twist between the first and third frequency energy values, determine a second twist between the second and fourth frequency energy values, and compare the first and second twists to determine the presence of the first and second tones.