A reverse power feeding powering sourcing equipment PSE in electrical communication with a power source and a distribution point unit DPU, the PSE comprising: a power output terminal; a control circuitry; and a detection and classification signal circuitry coupled to said power output terminal, wherein said detection and classification signal circuitry is arranged, responsive to said control circuitry, to: output a first detection signal exhibiting a voltage within a predetermined detection range; output a first classification signal exhibiting a voltage within a predetermined classification range; and output an additional signal, said additional signal exhibiting a voltage below a predetermined operating range, and wherein said control circuitry is arranged to: responsive to said output first detection signal, detect a valid signature resistance presented to said power output terminal; responsive to said output first classification signal, receive a first classification current at said power output terminal; responsive to said received first classification current, determine the class of the DPU; characterized in that said detection and classification signal circuitry is further arranged to: responsive to said output additional signal, detect the absence, or presence, of an off-hook phone coupled to said power output terminal; responsive to said detection of the absence of an off-hook phone, and further responsive to said valid signature resistance detection, output at said power output terminal power from a power source responsive to said determined class, said output power exhibiting a voltage within the predetermined operating range; and responsive to said detection of the presence of an off-hook phone, not output at said power output terminal power from the power source. a power output terminal; a control circuitry; and a detection and classification signal circuitry coupled to said power output terminal, wherein said detection and classification signal circuitry is arranged, responsive to said control circuitry, to: output a first detection signal exhibiting a voltage within a predetermined detection range; output a first classification signal exhibiting a voltage within a predetermined classification range; and output an additional signal, said additional signal exhibiting a voltage below a predetermined operating range, and output a first detection signal exhibiting a voltage within a predetermined detection range; output a first classification signal exhibiting a voltage within a predetermined classification range; and output an additional signal, said additional signal exhibiting a voltage below a predetermined operating range, and wherein said control circuitry is arranged to: responsive to said output first detection signal, detect a valid signature resistance presented to said power output terminal; responsive to said output first classification signal, receive a first classification current at said power output terminal; responsive to said received first classification current, determine the class of the DPU; responsive to said output first detection signal, detect a valid signature resistance presented to said power output terminal; responsive to said output first classification signal, receive a first classification current at said power output terminal; responsive to said received first classification current, determine the class of the DPU; characterized in that said detection and classification signal circuitry is further arranged to: responsive to said output additional signal, detect the absence, or presence, of an off-hook phone coupled to said power output terminal; responsive to said detection of the absence of an off-hook phone, and further responsive to said valid signature resistance detection, output at said power output terminal power from a power source responsive to said determined class, said output power exhibiting a voltage within the predetermined operating range; and responsive to said detection of the presence of an off-hook phone, not output at said power output terminal power from the power source. responsive to said output additional signal, detect the absence, or presence, of an off-hook phone coupled to said power output terminal; responsive to said detection of the absence of an off-hook phone, and further responsive to said valid signature resistance detection, output at said power output terminal power from a power source responsive to said determined class, said output power exhibiting a voltage within the predetermined operating range; and responsive to said detection of the presence of an off-hook phone, not output at said power output terminal power from the power source.