Abstract: An apparatus for testing and teaching the lifting capacity and technique of a user includes a brake or clutch for resisting user input force which is controlled by feedback from sensors through a computer. Several operating modes can be chosen, including isometric, isokinetic, isotonic and a special accommodating isotonic which simulates lifting a real object as long as the user exerts enough force, but decreases a resisting force when it is more than the user can handle. A motor is used to substantially eliminate inherent system resistance.

Abstract: An ultrasonic sensor system particularly for automatic door openers of a swinging door type, in addition to sensors (14) for people approaching a door for controlling opening and closing purposes, has at least one microprocessor controlled ultrasonic beam transducer (40, 41) for projecting an expanded unidirectional ultrasonic beam in a selected detection zone in the path of the swinging door and an ultrasonic detector for converting reflected ultrasonic beam energy into an analog electrical signal which constitute an acoustical image of objects in and bounding the selected detection zone. This acoustical image is stored or, a number characterized thereof is stored and this acoustic image is then compared with a later acoustical image of an object in the selected detection zone and then the comparison is used to signal a lack of correlation between the first and second acoustical images to produce a signal preventing operation of the door opening.

Abstract: Thin film radiant energy converter having a sputtered CdSiAs.sub.2 photovoltaic absorber layer and a thermally evaporated CdS top layer. The sputtering technique with multiple targets (Cd, Si, As) is used to obtain stoichiometric CdSiAs.sub.2 thin films which are polycrystalline and have large grain size to thereby reduce grain boundary recombinations of the photogenerated electrons.