New electronic devices such as the silicon rectifier, transistor, silicon controlled rectifier, and miniature electromagnetic relay are changing the complexion of aircraft d-c generating systems. Their application has resulted in the introduction of a static equivalent of the familiar carbon pile regulator and of the overvoltage relay, as well as a unique protector against feeder faults. As developed by General Electric, these new products provide better voltage regulation, improved engine starts, and better system protection. They are smaller, lighter, and longer-lived than the older electromechanical devices. Brushless d-c generators, also made possible through the use of modern semiconductors, bring relief from old-time maintenance problems of brush and commutator wear. All these new products represent new trends in aircraft d-c systems.