Patent ID: 8375231

Claim:
A power source equipment (PSE) device comprising: an interface adapted to couple to a network cable; a detector coupled to the interface and configured to measure a current flowing through the network cable and to generate a first measurement signal during a first period of time and a second measurement signal during a second period of time in response to measuring the current; a power circuit coupled to the interface; and a power classification circuit coupled to the detector and to the power circuit, the power classification circuit configured to control the power circuit to apply a power classification signal to the interface, the power classification signal having a substantially constant voltage level during the first period of time and, after the first period of time, having a time-varying voltage level around the substantially constant voltage level during the second period of time, the power classification circuit to determine the power classification of a device coupled to the network cable from a plurality of power classifications in response to the first measurement signal and the second measurement signal.