Abstract: To establish communications between a plurality of functional modules installed in a local unit and at least one Ethernet type external, multiplexed, multi-transmitter and multi-receiver bus enabling communications with other local units, the device according to the invention comprises as many internal buses as there are functional modules of the local unit, each internal bus being of the multiplexed, multi-transmitter and multi-receiver type, complying with the format of the information elements travelling through the external bus, said functional modules being coupled to the internal buses so that access to each internal bus is controlled by only one module; and at least one coupling module designed to provide for the transfer of information elements between the internal buses and the external bus.