Reverse power feeding power sourcing equipment and method

A reverse power feeding PSE in electrical communication with a DPU, the PSE constituted of: a control circuitry; and a detection and classification signal circuitry, arranged to: output a detection signal; output a classification signal; and output an additional signal exhibiting a voltage below an operating range, and wherein the control circuitry is arranged to: responsive to the output first detection signal, detect a valid signature resistance; responsive to the output first classification signal, receive a classification current and determine the class of the DPU; responsive to the outputadditional signal, detect the absence, or presence, of an off-hook phone; responsive to the detection of the absence of an off-hook phone, and further responsive to the detection of the valid signature resistance, output power exhibiting a voltage within the operating range; and responsive to the detection of the presence of an off-hook phone, not output power. 种与DPU处于电通信的反向馈电PSE，该PSE包括：控制电路系统；以及检测和分级信号电路系统，其被安排成：输出检测信号；