Patent ID: 7203851

Claim:
A first network device for supplying power to a second network device in communication therewith comprising: a first transformer in communication with the second network device; a second transformer in communication with the second network device; a switch; a power supply in communication with first and second transformers via said switch; a physical layer device comprising: a transmitter in communication with said first transformer; a receiver in communication with said second transformer; a signal generator in communication with said transmitter; a detector in communication with said receiver; and a controller in communication with said switch, said signal generator and said detector; wherein said signal generator generates a test signal comprising n sub-pulses to be transmitted by said transmitter, wherein n being greater than 2; and wherein when said detector, in response to said receiver, detects j pulses which are greater than a predetermined threshold, 1≦j<n, said controller, responsive to said detector, enables said switch to supply power from said power supply to the second network device.