Patent ID: 7355416

Claim:
A method of determining impedance between a power sourcing equipment and a powered device, the method comprising: supplying power to the powered device from the power sourcing equipment over a communication cabling at a first current limited level, I lim1 ; measuring, at a plurality of times in relation to the beginning of said supplying power, a voltage associated with the output of the power sourcing equipment; determining a minimum voltage, V min1 , of said measured plurality of voltages; determining an associated time, t min , of said determined V min1 in relation to said beginning of said supplying power at said I lim1 ; removing, subsequent to said supplying power at said I lim1 , said supplied power from the powered device; subsequent to said removing, supplying power to the powered device from the power sourcing equipment over the communication cabling at a second current limited level, I lim2 , said I lim2 being different than said I lim1 ; measuring, at said determined associated time t min in relation to the beginning of said supplying power at said I lim2 , a voltage associated with the output of the power sourcing equipment, V min2 ; and determining an impedance responsive to said V min1 , V min2 , I lim1 and I lim2 .