1. Method for implementing the training phase of adaptive channel equalization on a digital communications path, whereby during the normal data transmission state the method uses a predetermined symbol constellation and comprises the steps of coding the outgoing bit stream into symbols, using either QAM or CAP as the modulation of the line code, compensating for channel distortion by means of a linear equalizer (FFE) and a decision-feedback equalizer (DFE) or a Tomlinson-Harashima precoder (TML) or both of the latter (DFE and TML), thus permitting recovery of symbols passed through the channel ( 2, CHN) and the signal-processing means of the receiver into the original bit stream, characterized in that the transmitter (TX) or the receiver (RX) or both use bandstop filters forming at least one stop band on the signal spectrum and in which method the training of adaptive equalizers to the channel distortion is performed entirely or partially using a sparse symbol constellation, wherein the number of symbol states (S) is reduced from that of the symbol constellation used in the normal data transmission state.