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