Abstract: A system for sending uplink control signals to antennas and receiving downlink signals therefrom, where the uplink signals may be used to control antenna position and operate antenna switches and the like, and the downlink signals may indicate antenna position, the uplink signals being in the form of digital signals having two voltage levels within the range of a DC supply superimposed on the RF signals on the antenna feeder, and the downlink signals being digital signals in the form of changes in the DC current on the feeder, generated by a load having two resistance values.