Precise regulation of the direct current which provides power for the undersea repeaters in the new transatlantic telephone cable is necessary to maintain proper transmission levels and to assure maximum repeater valve life. The highest possible degree of protection is needed against excessive currents and voltages under a wide variety of possible fault conditions. Furthermore, to minimize the dielectric stresses, a double-ended series-aiding power feed must be used and the balance of these applied voltages must be maintained in spite of substantial earth potentials. The paper describes the design features which were employed to attain these objectives simultaneously, while eliminating, for all practical purposes, any possibility of even a brief system outage due to power failure.