A system and method for conveying supervisory signaling and power over the same twisted wire pairs in a cable as are used to carry data communications in accordance with a predetermined communications protocol. Supervisory signals having first and second differential components are generated. The first component is coupled to both wires of one of the twisted wire pairs as a common mode signal and the second component of the supervisory signal is coupled to both wires of another twisted pair as a common mode signal. The first and second components are recovered at the remote end of the cable. Physical interfaces are AC coupled to the respective twisted pairs at both ends of the cable and positive and negative voltage rails powered by a power sourcing device are coupled to predetermined twisted pairs to convey a DC voltage over the cable which may be used to power a remote electronic device.