A transmission device includes a first connecting module for connecting a DC/DC power converter to a telephone wire line or to a CPE wire line, and a second connecting module between the telephone and CPE wire lines, a detection module configured to detect a power feeding request signal on the CPE wire line, and a switching module configured to controls the second connecting module in its open state, and send a power ready signal on the CPE wire line, and a not control the second connecting module and not send a signal on the CPE wire line in a standby-by state, so that a total power consumption of the detection and switching modules is lower than a threshold in a stand-by state and higher in the active state, and the detection module is configured to control the switching module in response to a detection of the power feeding request signal.