Traditionally, shipboard power generation is accomplished via auxiliary engines and generator sets. Significant cost advantages can be projected if this electrical demand could be met by extracting power from the ship's prime mover. To accomplish this, and to maintain a constant frequency on thegenerator while the speed of the prime mover varies over a wide range, this contractor proposes the use of a diff differentially coupled epicyclic gear. Preliminary l laboratory testing of a differential gear by ttc has d demonstrated the ability of maintaining the output speed of a differential within very close limits, thus offering a solution to the previously identified and unsolved problem.