Readings present the effective voltage depending on the common worth of samples more than a whole quantity of intervals of the basic frequency Ca?ch ?ô?i ve? tru?ng th???ng x? s? mi?n Nam an toa?n nhâ?t chi?nh la? b?n hãy mang t?? ve? sô? ?o? ?ê?n t?i tru? s?? cu?a