Abstract: The present invention relates to a method of using a modem for processing signals for signal transmission in the base band on a two-wire line. In order to reduce coupling to adjacent channels in the two-wire line, and to reduce effective line attenuation, it is proposed that the signal that is to be transmitted in a process of the above type be encoded such that each three transmit bits are combined to form a tri-bit, and one of eight discriminable sender levels for a main data channel are associated with each tri-bit, whereby the modulation rate of the symbols on the line is reduced to one-third of the bit rate.