 The sections of the hypothetical infinite filter are made of series elements having impedance 2Z and shunt elements with admittance 2Y . The factor of two is introduced for mathematical convenience , since it is usual to work in terms of half @-@ sections where it disappears . The image impedance of the input and output port of a section will generally not be the same . However , for a mid @-@ series section ( that is , a section from halfway through a series element to halfway through the next series element ) will have the same image impedance on both ports due to symmetry . This image impedance is designated ZiT due to the " T " topology of a mid @-@ series section . Likewise , the image impedance of a mid @-@ shunt section is designated ZiΠ due to the " Π " topology . Half of such a " T " or " Π " section is called a half @-@ section , which is also an L @-@ section but with half the element values of the full L @-@ section . The image impedance of the half @-@ section is dissimilar on the input and output ports : on the side presenting the series element it is equal to the mid @-@ series ZiT , but on the side presenting the shunt element it is equal to the mid @-@ shunt ZiΠ . There are thus two variant ways of using a half @-@ section . 
 The sections of the hypothetical infinite filter are made of series elements having impedance 2Z and shunt elements with admittance 2Y . The factor of two is introduced for mathematical convenience , since it <a href='drop_aux' title='1'><mark>is</mark></a>usual to work in terms of half @-@ sections where it <a href='uninflect' title='2'><mark>disappears</mark></a> . The image impedance of the input and output port of a section will generally <a href='negative_concord' title='3'><mark>not</mark></a><a href='negative_concord' title='4'><mark>be</mark></a> the same . However , for a mid @-@ series section ( that is , a section from halfway through a series element to halfway through the next series element ) will have the same image impedance on both ports due to symmetry . This image impedance is designated ZiT due to the " T " topology of a mid @-@ series section . Likewise , the image impedance of a mid @-@ shunt section is designated ZiΠ due to the " Π " topology . Half of such a " T " or " Π " section is called a half @-@ section , which <a href='drop_aux' title='5'><mark>is</mark></a>also an L @-@ section but with half the element values of the full L @-@ section . The image impedance of the half @-@ section is dissimilar on the input and output ports : on the side presenting the series element it is equal to the mid @-@ series ZiT , but on the side presenting the shunt element it <a href='drop_aux' title='6'><mark>is</mark></a>equal to the mid @-@ shunt ZiΠ . <a href='dey_it' title='7'><mark>There</mark></a> are thus two variant ways of using a half @-@ section . 
The sections of the hypothetical infinite filter are made of series elements having impedance 2Z and shunt elements with admittance 2Y . The factor of 2 is introduced fir mathematical convenience , since it usual to wrk in terms of half @-@ sections where it disappear . da image impedance of tdainput and output port of a section will generally ain't the same . However , for a mid @-@ series section ( that is , a section from halfway thru a series element to halfway through the nxt series element ) gon have thdaame image impedance on both ports due to symmetry . This image impedance is designated ZiT due to the " T " topology of a mid @-@ series section . Likewise , the image impedance of a mid @-@ shunt section is designated ZiΠ due to thedaΠ " topology . Half of such a " T " or " Π " section is called a half @-@ section , which also an L @-@ section but with half the element values of the full L @-@ section . The image impedance of the half @-@ section is dissimilar on the daut and output ports : on the sda presenting the series element it is equal to the mida-@ series ZiT , but on the side presenting the shunt element it equal to the mid @-@ shunt ZiΠ . It is thus two variant ways of usin a half @-@ section .