Abstract: A power status monitor for an electronic system includes a charge/discharge model of the system power supply. The charge/discharge model contains an estimate of the amount of time during which energy-storage devices in a system DC power supply are capable of maintaining system operation following loss of AC power. The power status monitor monitors the frequency and an amplitude of the voltage of the AC power source for signs indicating imminent failure of the AC power source. In the event that such signs are detected, the estimate in the charge/discharge model is decremented at a rate corresponding to the rate at which charge is consumed. A trip value, applied to the charge/discharge model, determines the time at which a signal is generated enabling an orderly shutdown of the system load. If acceptable AC power is resumed before the trip value is reached, the charge/discharge model increases its estimate of the time available at a rate corresponding to the charge accumulation in the DC power supply.

Abstract: Digital pixel values for each image frame are written onto pages of a disk buffer memory (DBM) under video frame timing and are read from memory and written on disk under disk timing. When the last page of the DBM is reached, readout is switched back to the first page. Only DBM locations for pixels within the circular boundaries of the image are addressed during reading and writing. Groups of adjacent pixels are written simultaneously on the several disks under control of clocks that are derived from disk. A circuit corrects for skew resulting from asynchronism between the disks. A converter converts serially recorded pixels of any bit length to parallel bits of the same number as before they were serialized. The commands for the disk drive are put in registers for one disk index pulse and they are ready for execution when the next index pulse occurs.

Abstract: An image displayed on a video monitor screen is surrounded with a uniform dark background. A multiplexer (MUX) has its output coupled to the monitor and one input coupled to a display controller memory for digitized image pixels and another input coupled to a switching circuit for simulating pixel bits which can be all zeros to produce black or dark pixels in the display. For each horizontal scan line the MUX is caused to select the black pixels until the image boundary is reached, then select image pixels until the opposite image boundary is reached and the black pixels are selected again to the end of the line.