Abstract: A hand-held device produces an omnidirectional beam of infra-red light which can be aimed by the user. A plurality of detectors positioned in a rectangular array adjacent a video monitor and each detector produces an electrical signal that varies as a function of the light intensity impinging thereon. A circuit compares the signals from the detectors to determine coordinates of a position on the monitor at which to place a cursor. A linear transfer function is applied to the detector signals before determining the coordinates. The coordinates are processed by a seventh order recursive digital filter and the resultant position must be a minimum distance from the present position before the cursor is relocated. By varying the direction of the light beam the cursor position can be changed. When the cursor is at the position desired by the user, the hand-held device is activated to produce a different light beam.

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.