The invention relates to a device for exchanging digital data between several sources and at least one hub in a CDMA system, characterized in that it comprises a number n of digital transmission/reception circuits (1) installed in parallel, each circuit (1) comprising a transmitter (2i) comprising means of generating an integer number Nc of codes that will be used for spectral spreading of data to be transmitted and a receiver (4i) comprising means (46, 48) of detecting the access of new sources to the CDMA system transmission channel and means (49) of generating synchronization signals and power control signals corresponding to each detected new source.