The present invention relates to a point-of-use water treatment system unit. The male buckle includes two resilient retainers disposed on two sides thereof, each resilient retainer has a positioning projection fixed on a front end thereof. On the other end of the housing is mounted a rotor. Compared to software guards, hardware support for CFI and XFI increases the efficiency and simplicity of enforcement. The computing system calculates a difference value between the first value and the predetermined frequency value.