rapidly to be taken into account by the semi fixed equalizer an adaptive equalizer of the conventional type which operates according to known equalization algorithms is connected in series with the semi fixed equalizer fig9 shows an illustrated embodiment of the semi fixed equalizer it comprises a plurality of shift cells 80 1 to 80 k in which the sampled signal s mr to be equalized dwells the output of each cell is connected to an input of a multiplier 81 1 to 81 k which has another input connected to the selected weight factors h 34 1 to h 34 k the outputs of the multipliers are connected to a summator 85 which produces an equalized signal s eg1 the weight factors are updated intermittently according to the process described earlier the equalized signal s eg1 then enters the adaptive equalizer of a conventional type of which an example is shown in fig1 it comprises various shift cells 90 1 to 90 p in which the signal s eg1 to be equalized dwells the output of each cell is connected to an input of a multiplier 91 1 to 91 p which has another input connected to weight factors c k the outputs of the multipliers are connected to a summator 95 which produces an equalized signal s eg2 for computing the weight factors of the adaptive equalizer the computing means compt 30.