Abstract: A rapid palatal expansion device is provided having first and second housing parts joined by a threaded spindle which controls the relative position of those housing parts, the spindle incorporating a ratchet/stop system to prevent unwanted screw slippage or backwinding while exerting expansion force to the appliance. Each housing part includes at least one extending rod for transmitting the expansion force to the patient's teeth or body parts. The housing parts may be oriented with respect to each other by a pair of guide rods extending through them. Directional indicia may be formed on one or more of the housing parts to facilitate spindle adjustment by the orthodontist.

Abstract: A traveling wave tube incorporates a collector having a plurality of collector electrodes, one or more of which is operated at a potential below that of the cathode so as to collect electrons having associated energies greater than the cathode potential (E.sub.K), and thereby act as a high impedance current source. The current from the collector electrode operated below the cathode potential (E.sub.K) is converted by a power converter to an alternating current signal that can be either magnetically coupled to the high voltage transformer (T.sub.1) of the traveling wave tube power supply, or coupled to an external load with a transformer (T.sub.2), thereby improving the operating efficiency of the traveling wave tube system.