Adaptive transversal filter

An adaptive transversal filter having an input for receiving a time-discrete input signal which is representative of three signal levels constituting a central signal level and two extreme signal levels, first and second delay means responsive to said signal levels applied to said input for producing delayed versions of each time-discrete input signal, first and second coefficient registers each containing respective coefficients for the non-delayed and each delayed version of the input signal, individual coefficients in said first and second registers being respectively associated with signals in said first and second delay means;

• means responsive to said registers and to said first and second delay means for multiplying one of the coefficients by the associated version of the input signal, and means for adding together all the multiplying results obtained to provide a cancellation signal, characterized in that the first delay means contains M delayed versions of each time-discrete signal and the first coefficient register contains M+1 coefficients, that the second delay means contains N delayed versions of each time-discrete signal and the second coefficient register contains N+1 coefficients, wherein M.ltoreq.N and that when information representing the central signal level is applied to the first delay means, that information representing one or the other extreme signal level is correspondingly applied to the second delay means, in addition means being provided for only applying multiplication results obtained with the air of the first delay means to said adding means when the information present which signals the presence of the central signal level is applied to the first delay means.