The CEFALY BIOFEED records the action potential of the head muscles through an electrode placed on the forehead. There is a feedback mechanism which is both visual and auditory. The visual signal comes from the Light Emitting Diode (LED) on the device. The auditory signal is composed of very audible beeps: the frequency of the beeps decrease with the muscles’ action potential. So the patient can hear that he/she is relaxing as the beeps increase in interval.