Basic principle: Readings show the effective voltage based on the common worth of samples more than a whole number of durations of the elemental frequency  + B?n c?p nh?t th? công k?t qu? v? h? th?ng c?a mình: (nh?p n?i dung tr? tin nh?n sms, nh?p vào d? li?u ?ng d?ng, nh