Abstract: Before modulating the transmission carrier, each binary data signal is individually coded as a discrete symbol belonging to a PSK constellation of N symbols which are combined with N discrete points to produce two binary signal streams of which the first is in phase with the incoming signal while the second is in phase quadrature with said incoming signal. Each of said two binary signal streams is assigned its own signature by combining it with a discrete spreading code to produce two spread composite signal streams each of which is to be applied to a modulator. Both of said spreading codes are substantially orthogonally cross-correlated. The method may be used in a satellite communications system, in particular for digital sound transmission and communication via land microterminals.