a low noise d . c . power supply system that is particularly suited for suping d . c . power from a stationary source to electronics equipment mounted on a rotating assembly . brush and slip ring assemblies are used to transfer the d . c . power to the rotating assembly and brush noise is minimized by having non - inductive impedences on both sides of the brush and slip ring assemblies . floating circuits are employed to transfer the d . c . power from the stationary assembly to the rotating assembly with the return reference ground being through the brush and slip ring assemblies to the stationary assembly . higher than usual voltages are supplied to a capacitor mounted on the rotating assembly to charge the capacitor providing reserve energy storage , providing a voltage margin for further regulation and thus minimizing the effect of brush noise .