The paper discusses some of the difficulties encountered when extending the load capacity of vibratory convertors, and, in particular, those which are imposed by contact deterioration due to arcing. Two methods are described by which these difficulties may be overcome, both making use of special circuits designed to reduce the current carried by the contacts at the moment they break the circuit. Reference is also made to methods of dealing with certain vibrator defects, and with transformer surges. Finally, examples are given of practical applications of the circuits described.