Abstract: The switching network included in the system is connected to circuit mode and/or packet mode mono- or multi-channel digital lines via connection modules. These modules enable the system connections to be standardized and accept thus any number of multiplexed channels in the lines and any transmission mode, namely duplex or half-duplex. The flag/packet transition in a packet mode channel is detected in a connection module and is transmitted as a particular word in a predetermined time interval of the outgoing multiplex of this module, at the same time as the address of the channel, thereby precluding the use of purpose-built links.