Basic principle: Readings display the productive voltage dependant on the common value of samples over a whole variety of intervals of the fundamental frequency ?? ng??i ch?i mua X? s? MB ti?n theo dõi l?ch m? th??ng và KQXSM mi?n b?c, Ketqua.tv c?p nh?t l?ch m? th??ng XSKT mi?n b?c