Patent ID: 7656956

Claim:
A method of transmitting supervisory signals and providing power over a cable having first and second ends, said cable including at least first and second twisted pairs, said method comprising the steps of: ac coupling physical interfaces operative in accordance with a predetermined data communication protocol to each of said twisted pairs at one end of said cable to permit data communication over the respective twisted pair via said predetermined protocol; generating first and second differential signal components from a first supervisory signal, wherein said first and second differential components are DC isolated from said first supervisory signal; coupling said first differential signal component to both wires of said first twisted pair at said first end of said cable such that said first differential signal component is superimposed on both wires of first twisted pair as a first common mode signal; and coupling said second differential signal component to both wires of said twisted pair at said first end of said cable such that said second differential signal component is superimposed on both wires of said second twisted pair as a second common mode signal, wherein said step of generating said first and second differential signal components comprises the steps of coupling said first supervisory signal to a primary winding of a first signaling transformer having said primary winding and a center-tapped secondary winding, and obtaining said first and second differential signal components from respective ends of said secondary winding of said first signaling transformer, wherein said cable includes at least one additional wire, said method further including the steps of: coupling a first rail of a power supply having first and second voltage rails to both wires of said first and second twisted pairs at said one end of said cable; and coupling said second rail of said power supply to said at least one additional wire at said one of said first and second ends of said cable, and wherein said cable further includes third and fourth twisted pairs and said first power supply rail coupling step comprises the step of coupling said first power supply rail to said center-tap of said secondary winding of said first signaling transformer to dc couple said first power supply rail to both wires of said first and second twisted pairs and said second power supply rail coupling step comprises the step of coupling said second power supply rail to a center-tap of a secondary winding of a second signaling transformer to dc couple said second power supply rail to both wires of said third and fourth twisted pairs, said second signaling transformer having said center-tapped secondary winding and a primary winding, said secondary winding of said second transformer having respective ends coupled to center-taps of third and fourth inductors, said third and fourth inductors having respective ends coupled to the wires of said third and fourth twisted pairs respectively.