Patent ID: 9100070
Filing Date: 2015-08-04
Classification: G01R,H03F,H04B,H04L

Abstract:
1. A network interface card comprising: a power supply configured to produce a direct current (DC) power signal; a data transmission circuit that receives digital data for transmission over a network cable to a remote location, the data transmission circuit operating to convert the received digital data to a differential voltage; an isolation transformer having a primary winding coupled with the data transmission circuit to receive the differential voltage, a center tap coupled to the power supply to receive the DC power signal, and a secondary winding configured for coupling to the network cable to provide a composite signal to the network cable, the composite signal being a superposition of the DC power signal for powering a device through the network cable and the differential voltage for communicating information to a receiver on the network cable, the isolation transformer having a variable impedance which varies with the DC power signal in the isolation transformer; and a circuit coupled with the data transmission circuit and the isolation transformer and that detects variations in the variable impedance of the isolation transformer, wherein the circuit comprises a time domain reflectometer configured to cause the isolation transformer to discontinue the composite signal if the time domain reflectometer detects a reduction in the variable impedance of the isolation transformer.