Abstract: A display system and method utilizing a common character generator among a plurality of display devices. Each display device generates address signals which are multiplexed and applied to the character generator. The output from the character generator is used to control the visual representation produced by each display device. A graphics memory of picture elements can be addressed for a composite display of graphics and alphanumeric characters by the various display devices.

Abstract: A video display memory expansion system for expanding the graphics memory within the video display. The memory expansion system is suited for increasing the resolution of a graphics display from a low-resolution to a high-resolution display. A video display device is adapted to receive a relatively simple graphics memory expansion accessory to thereby easily and inexpensively provide the increased graphics memory capability.

Abstract: A photomultiplier detector protection system and method utilizing a negative feedback loop to maintain the photomultiplier detector output below a predetermined output. The feedback loop comprises a comparator responsive to the photomultiplier detector output and also responsive to a predetermined limit signal. The comparator output is applied to a summing amplifier which also receives a voltage adjust signal. The output of the summing amplifier controls the output of a power supply which is in turn applied to the photomultiplier detector.

Abstract: Apparatus for indicating when an analog or digital input signal remains sufficiently stable for a predetermined length of time. The apparatus continuously monitors the input signal instead of sampling it only at discrete points in time. The apparatus includes a memory which stores the value of the input signal at the time of the most recent occurrence of a reset signal, a comparator which produces the reset signal whenever the input signal differs from the memory signal by an amount greater than that allowed by a predetermined comparison criterion, and a timer for indicating that the input signal is stable when the reset signal has not been produced for a time exceeding the predetermined length of time.