 The filters were designed by Campbell for the purpose of separating multiplexed telephone channels on transmission lines , but their subsequent use has been much more widespread than that . The design techniques used by Campbell have largely been superseded . However , the ladder topology used by Campbell with the constant k is still in use today with implementations of modern filter designs such as the Tchebyscheff filter . Campbell gave constant k designs for low @-@ pass , high @-@ pass and band @-@ pass filters . Band @-@ stop and multiple band filters are also possible . 
 The filters <a href='uninflect' title='1'><mark>were</mark></a> designed by Campbell for the purpose of separating multiplexed telephone channels on transmission lines , but their subsequent use <a href='uninflect' title='2'><mark>has</mark></a> been much more widespread than that . The design techniques used by Campbell <a href='been_done' title='3'><mark>have</mark></a> largely been superseded . However , the ladder topology used by Campbell with the constant k <a href='drop_aux' title='4'><mark>is</mark></a>still in use today with implementations of modern filter designs such as the Tchebyscheff filter . Campbell gave constant k designs for low @-@ pass , high @-@ pass and band @-@ pass filters . Band @-@ stop and multiple band filters <a href='drop_aux' title='5'><mark>are</mark></a>also possible . 
Da filters was designed by Campbell for the purpose of separating multiplexed telephone channels on transmission lines , but their subsequent use have been much more widespread than that . The design techniques used by Campbell done largely been superseded . However , tdaladder topology used by Campbell with the constant k still in use today with implementations of modern filter designs such as the Tchebyscheff filter . Campbell gave constant k designs fir low @-@ pass , high @-@ pass and band @-@ pass filters . Band @-@ stop and multiple band filters also possible .