Abstract: A method for communicating with a plurality of radio frequency (RF) devices includes transmitting a first signal at a first power level, interrogating RF devices responding to the first signal, instructing the responding RF devices to change state, and transmitting a second signal at a second power level higher than the first power level. The RF devices responding to the first signal do not respond to the second signal upon changing state.

Abstract: A data communications network for delivering power and communications over the same cable bundle includes a plurality of communications nodes wherein associated with each of the nodes is a transformer having a core, a primary winding and a secondary winding. The secondary winding has a centertap connection which either splits or merges the current in the secondary winding to eliminate net DC flux within the transformer. A DC/DC converter is also included for transforming the relatively high DC voltage of the cable down to a regulated supply potential for use by that node. The converter is coupled between the centertap of the transformer and the cable bundle. A power source provides the DC voltage distributed across the network and is coupled to the cable bundle via a centertap connection of another winding.