 Several L @-@ shape half @-@ sections may be cascaded to form a composite filter . Like impedance must always face like in these combinations . There are therefore two circuits that can be formed with two identical L @-@ shaped half @-@ sections . Where a port of image impedance ZiT faces another ZiT , the section is called a Π section . Where ZiΠ faces ZiΠ the section so formed is a T section . Further additions of half @-@ sections to either of these section forms a ladder network which may start and end with series or shunt elements . 
 Several L @-@ shape half @-@ sections may be cascaded to form a composite filter . Like impedance must always face like in these combinations . <a href='dey_it' title='1'><mark>There</mark></a> are therefore two circuits <a href='null_relcl' title='2'><mark>that</mark></a>can be formed with two identical L @-@ shaped half @-@ sections . Where a port of image impedance ZiT <a href='uninflect' title='3'><mark>faces</mark></a> another ZiT , the section is called a Π section . Where ZiΠ <a href='uninflect' title='4'><mark>faces</mark></a> ZiΠ the section so formed <a href='drop_aux' title='5'><mark>is</mark></a>a T section . Further additions of half @-@ sections to either of these section <a href='uninflect' title='6'><mark>forms</mark></a> a ladder network which may start and end with series or shunt elements . 
Several L @-@ shape half @-@ sections may b cascaded to form a composite filter . Like impedance must always face like in these combinations . It is therefore 2 circuits can bbformed with tw2dentical L @-@ shaped half @-@ sections . Where a port of image impedance ZiT face another ZiT , da section is called a Π section . Where ZiΠ face ZiΠ the section soo formed a T section . Further additions of half @-@ sections to either of these section form a ladder network which may start and end wid series or shunt elements .