1. A system of the type for transmitting data signals at a given symbol rate 1/T from a data transmitter to a data receiver through a channel of a transmission facility having a plurality of channels; the data transmitter comprising a data signal source connected to the said channel through a data encoder and a transmit filter; said channel being a dispersive transmission channel of a substantially minimum-phase character, this transmission channel introducing into the transmitted data signal inter symbol interference as well as noise and crosstalk from similar data signals in the remaining channels of the transmission facility; and the data receiver comprising an equaliser of the decision feedback type which includes a feedforward filter connected between said channel and a first input of a difference circuit, a data signal regenerator connected to the output of the difference circuit and controlled by the symbol rate 1/T recovered from the transmitted data signal, and a feedback filter connected between the output of the data signal regenerator and a second input of the difference circuit, characterized in that the feedforward filter comprises a low-pass filter section having a substantially minimum-phase character and an amplitude-frequency characteristic .vertline.W(f).vertline. which has a pronounced maximum .vertline.W(f.sub.m).vertline. for a frequency f.sub.m near the frequency f=1/((N+1)T), where NT is the memory span of the feedback filter corresponding with a number of N consecutive data symbols, the value .vertline.W(f.sub.m).vertline. of this maximum being greater as the memory span of the said channel is larger and as the number N is smaller, and the amplitude-frequency characteristic .vertline.W(f).vertline. substantially decreasing gradually for frequencies exceeding f.sub.m.