Patent ID: 7451329

Claim:
In an apparatus connected to a remote device through a data communications cable, a method for provisioning power for the remote device, the method comprising: providing a first electrical stimulus to the data communications cable and the remote device, and sensing a first electrical response to the first electrical stimulus from the data communications cable and the remote device; providing a second electrical stimulus to the data communications cable and the remote device, and sensing a second electrical response to the second electrical stimulus from the data communications cable and the remote device, the second electric stimulus being different than the first electrical stimulus; and identifying a power demand for the data communications cable and the remote device, the power demand being based on the first and second electrical responses; wherein the first electrical stimulus is a first voltage, V 1 ; wherein the second electrical stimulus is a second voltage, V 2 ; wherein the first electrical response is a first current, I 1 ; wherein the second electrical response is a second current, I 2 ; and wherein identifying the power demand includes: ascertaining a resistance, R CABLE , of the data communications cable where R CABLE = V 1 × I 1 - V 2 × I 2 ( I 1 ) 2 - ( I 2 ) 2 , and assessing power loss through the data communications cable based on the resistance, R CABLE .