Abstract: A modular display system is disclosed for displaying a map, graph, chart or other planar graphic representation in a plurality of planar modules capable of being disposed in a planar contiguous array having a smooth, markable surface. Each module is formed of a generally rectangular planar base portion having a plurality of planar projecting tongues and planar grooves, a rectangular portion of a map, graph, chart or other planar graphic representation, and a rectangular planar transparent cover portion. The aligned attachment of a base portion, a graphic portion, and a cover portion using adhesive forms a module. By temporary interlocking planar arrangement of modules, with tongues and grooves of each base portion in mating disposition with the grooves and tongues of other base portions, a planar surface is provided with the graphic portions capable of being viewed through the cover portions.

Abstract: A control system to control a glow discharge apparatus, as for ion nitriding, utilizing operator selected parameters. Normally, the control system in an automatic state sequences through a glow discharge process by progressively changing modes. The sequence includes an idle mode, a pumpdown mode, a warming mode, a processing mode, a cooldown mode, and a cycle complete mode. The sequence can be interrupted by the control system to provide a plurality of special states, other than the automatic state, including a manual state, a hold state, a manual reentrant state, a power supply shutdown state, or a furnace shutdown state. While in the processing mode the control system regulates the pressure of an ionized gas in a chamber and the temperature of a workpiece within the chamber.