A first network device supplies power to a second network device in communication therewith. The first network device comprises a physical layer device which includes a pulse generator to generate a test signal comprising n sub-pulses to be transmitted to the second network device, wherein in n being greater than 2. A detector is responsive to the second network device, and a controller is in communication with the detector and the pulse generator. When the detector detects j pulses which are greater than a predetermined threshold, 1.ltoreq.j