The invention relates to a device for interconnecting at least two data-communication networks, connecting a first network qualified as a high-security network and at least one second network qualified as a low-security network, the device including a one-way channel referred to as downlink channel between the high-security network and the low-security network, and a one-way channel referred to as uplink channel between the low-security network and the high-security network, the uplink channel being configured, in accordance with at least one predetermined data model from the low-security network or a dedicated loading channel, such as to transmit a return signal towards the high-security network whenever an uplink data stream sent from the low-security network to the high-security network includes all or part of the predetermined data model, the return signal being transmitted together with a transmission of the uplink data stream or at the end of a transmission of the uplink stream towards the high-security network.