A host device capable of communicating with an external network. The host device may comprise a power-application unit and a network interface. The power-application unit may receive from a power-supply unit a first power-supply output having a first voltage level and a second power-supply output having a second voltage level. The power-application unit may be controllable for producing selectively a first power-application output having a third voltage level from the first power-supply output and a second power-application output having a fourth voltage level from the second power-supply output. The network interface may transmit data to and receive data from an external network, and may be powered at least in part by the first and second power-application outputs.