Abstract: A matrix display drive circuit is disclosed which generates multilevel and multiphase, time-variant drive waveforms for driving the rows and columns of a ferrolectric liquid crystal matrix display. The circuit can provide up (write) and down (erase) pulses selectively to each pixel of the display using standard twisted-nematic type liquid crystal display drivers. A complex waveform generator provides multilevel, multiphase control signals to the supply voltage inputs of the drivers. Timing and synchronizing signals are extracted from the graphics data and timing source outputs to allow such multilevel, multiphase signals as may be required for the effective multiplexing of the display matrix.

Abstract: Apparatus for retaining axial mandrel movement relative to a cylindrical housing. A cylindrical housing has an open longitudinal passageway therethrough and a circulation port disposed through a wall thereof. A valve mandrel is slidably received in the housing and is moveable between a position in which fluid may be circulated only between the passageway and the exterior of the housing, a position in which fluid may be circulated only between the exterior of the housing and the passageway and a position in which fluid may not be circulated in either direction. An annular piston is operatively connected to the valve mandrel and has a first side exposed to the pressure exterior of the housing and a second side exposure to the pressure interior of the housing to permit movement of the valve mandrel to its various positions by application of pressure to the interior and exterior of the housing.

Abstract: Pressure operated circulation valve and method for using the same. A cylindrical housing has an open longitudinal passageway therethrough and a circulation port disposed through a wall thereof. A valve mandrel is slidably received in the housing and is moveable between a position in which fluid may be circulated only between the passageway and the exterior of the housing, a position in which fluid may be circulated only between the exterior of the housing and the passageway, and a position in which fluid may not be circulated in either direction. An annular piston is operatively connected to the valve mandrel and has a first side exposed to pressure exterior of the housing and a second side expose to pressure interior of the housing to permit movement of the valve mandrel to its various positions by application of pressure to the interior and exterior of the housing.