Patent ID: 6370244
Filing Date: 2002-04-09
Classification: H04M,H04Q

Abstract:
A method for detection of DTMF symbols in a signal, comprising the steps of:detecting the power at each DTMF frequency; analyzing the detected power to determine whether a DTMF symbol has been received; and analyzing the detected power to determine whether the signal representing the symbol satisfies specified timing constraints; wherein the step of analyzing the detected power to determine whether the signal satisfies specified timing constraints further comprises: analyzing the detected power in each frame of a succession of frames to determine whether the signal is greater than a first specified duration; analyzing the detected power in each of said frames to determine if the signal is less than a second specified duration; wherein said second specified duration is greater than said first specified duration; analyzing the detected power in each of said frames to determine if the signal is not interrupted for a duration of time that is greater than or equal to a third specified duration; and analyzing the detected power in each frame of said frames to determine if the signal is not interrupted for a duration of time that is greater than or equal to a fourth specified duration; wherein said fourth specified duration is greater than said third specified duration.