Technique for providing power to a powered device (PD) over a cable having first and second sets of twisted pairs, such as signal pairs and spare pairs. Power Sourcing Equipment (PSE) circuitry is coupled via a first switch to the second set, e.g. to the spare pairs. A switch control circuit turns the first switch off to enable the PSE circuitry to perform a prescribed operation in connection with the PD over only the first set, e.g. over the signal pairs, and turns the first switch on to enable the PSE circuitry to perform the prescribed operation in connection with the PD over the first and second sets.