Post #1203890

@dzwiedziu That 750Hz could be an artifact of the DSP in the headphone design, or even something as simple as the casing around the microphone causing a notch filter (not as dramatic as what they show in the video). I would expect it to be different across different manufacturers. If 770Hz is close enough, then playing the DTMF for 666 loud over a Bluetooth speaker should also work!