Readings display the effective voltage determined by the typical worth of samples about a whole quantity of intervals of the elemental frequency K?t Qu? X? S? K?t Qu? X? S? Mi?n Nam K?t Qu? X? S? Mi?n Trung K?t Qu? X? S? Mi?n B?c KQXS Các T?nh KQXS ?i?n Toán X? s? ?i?n toán M