Abstract: A reversible valve for selectively delivering a pressurized gaseous mixture to and exhausting it from a reversible air motor or other pressure operated device. The valve has a perforate piston actuated by introducing the pressurized gas to a through flow position closing off lateral exhaust ports and actuated by the pressurized gas and a spring to a position fully opening the exhaust ports when flow to the valve is reversed.

Abstract: An electrical control unit for interconnection between a source of electrical energy and an electrically driven unit including a slide surface composed in part of electrically nonconductive material, a plurality of conductive discrete contact elements arranged in the slide surface, a conductive liquid contact adapted to progressively engage certain of the conductive discrete contact elements in the slide surface to provide a variable magnitude electrical output, and/or one or more conductive liquid contacts adapted to engage other of the discrete contact elements in the slide surface to effect a switching operation with respect to the variable magnitude electrical output or other electrical signal.