Hi, I'm trying to detect North America RING_TONE using spandsp Using default settings as mentioned follows <tone name="RING_TONE" description="North America ring"> <element freq1="440" freq2="480" min="1200" max="0"/> </tone> But I'm not getting consistent tone detections. Is there any thing that I need to change to have a proper tone detection. As per the tone/spectrum analysis using audacity. This tone is having two frequencies 440 and 480 a mentioned in conf, but spandsp is not detecting them. To have a proper and consistent tone detection how much duration I should use? Please refer spectrum analysis of tone representing 440Hz & 480Hz frequencies. As per the doc min and max values represents duration. How to determine these durations of any give tone? What is the meaning of having max value 0 ? -- Thanks & Regards, Naveen Tamanam