A power source and control system is particularly suited for use in an outdoor landscape lighting system. The power source and control system includes at least one switching mode AC-to-DC power supply having an additional output stage for efficiently converting the DC output signal into another relatively low frequency AC signal for transmission to a plurality of buried power conductors. A Manchester encoded control signal is encoded at a relatively high frequency onto the AC signal sent over the buried power conductors so that intelligent LED lighting fixtures can be powered by the AC signal and selectively have their intensity changed when they decode the control signal.