The frequency spectrum of a transmitter system is spreaded in the transmitter (1) through the codification of information bits by means of sequence pairs of Golay complementary sequences. The spectrum is received in the receiver (2) and is subject to a filter, which is adapted to the features of such sequences enabling the detection of digital levels corresponding to the original transmitted information. If pairs of orthogonal sequences, A amplitudes for modulating data, and N-PSK modulation are used, it is possible to get a transmission speed (C) equal to:Where B is to the null-to-null spread bandwidth used in Hertz. It allows an improvement in quality as compared to other digital-communication systems, which use spread spectrum techniques and CDMA, obtaining a process gain independent of the transmission speed.