Abstract: A bit-by-bit time-division digital switching network switches a plurality of incoming and outgoing isochronous digital data channels having rates which are different but sub-multiples of a given low rate. After phasing said incoming digital channels, bits having a predetermined binary state are detected. Previously stored address words of said outgoing digital channels to be switched to said incoming digital channels are read-out and correspond to switched incoming channels whose detected bits have said predetermined binary state. Then the read outgoing channel address words are multiplexed into a multiplex digital highway at high rate. In the transmission part of each outgoing digital channel address words of said outgoing digital channel are detected. A bit at said predetermined binary state or a bit in the other binary state is transmitted on the outgoing digital channel in response to the detection or failure of detect the address word of said outgoing digital channel.