Patent ID: 7599485

Claim:
A communications system comprising: a first communications device operative to supply power at an interface; and a second communications device coupled to the interface of the first communications device via a multiple-conductor-pair cable; wherein the first communications device includes (1) a single-pair identity signal generator operative to generate a single-pair identity signal on one conductor pair of the cable, the single-pair identity signal having an amplitude greater than the amplitude of communications signals appearing on the conductor pair and substantially less than the amplitude of a power signal generated on the conductor pair by the first communications device, and (2) a single-pair sensor operative to sense a predetermined conduction characteristic of the conductor pair of the cable indicative of the presence of a single-pair identity circuit; and wherein the second communications device includes the single-pair identity circuit coupled to the conductor pair of the cable, the single-pair identity circuit being activated by the single-pair identity signal on the conductor pair to create the predetermined conduction characteristic of the conductor pair to be sensed by the single-pair sensor of the first communications device.