Thus , k will have units of impedance , that is , ohms . It is readily apparent that in order for k to be constant , Y must be the dual impedance of Z. A physical interpretation of k can be given by observing that k is the limiting value of Zi as the size of the section ( in terms of values of its components , such as inductances , capacitances , etc . ) approaches zero , while keeping k at its initial value . Thus , k is the characteristic impedance , Z0 , of the transmission line that would be formed by these infinitesimally small sections . It is also the image impedance of the section at resonance , in the case of band @-@ pass filters , or at ω = 0 in the case of low @-@ pass filters . For example , the pictured low @-@ pass half @-@ section has