POINT, CRITICAL PIXEL The smallest discrete scanning line sample of a facsimile system, which sample contains grayscale information. See also Pel. PLAN FOR LOGISTIC SUPPORT A major section of the mate- riel acquisition plan that deals with all aspects of materiel support planning. PLASMA A constricted electric arc-gas mixture. PLASMA-ARC WELDING An arc-welding process in which fusion is obtained by the heat of a constricted-arc plasma. PLASTIC DEFORMATION A change in dimensions of an object under load that is not recovered when the load is removed; opposed to elastic deformation. PLATED-THROUGH HOLE A hole in which electrical connec- tion is made between internal or external conductive patterns, or both, by the deposition of metal on the wall of the hole. PLATING BAR The temporary conductive path interconnecting areas of a printed board to be electroplated, usually located on the panel outside of the borders of such a board. PLATING LOT A plating lot is defined as any number of printed wiring boards or composite panels that are placed in any one plat- ing tank and are processed through that one particular plating cycle. PLATING UP The process consisting of the electrochemical depo- sition of a conductive material upon the base material (surface holes, etc.) after the base material has been made conductive. PLENUM Within a building, a space created by building compo- nents, designed for the movement of environmental air; e.g., a space above a suspended ceiling or below an access floor. PLOTTING The practice of mechanically converting X-Y posi- tional information into a visual pattern, such as artwork. PLUG WELD A circular weld made through a hole in one member of a lap or T-joint fusing that member to the other. The walls of the hole may or may not be parallel, and the hole may be partially or completely filled with weld metal. POGO EFFECT The result of inharmonic surging of propellants in a guided missile fuel system, producing an extreme vertical force due to analomic pressures. POINT, CRITICAL A point in a subsystem considered most sus- ceptible to interference due to sensitivity, inherent susceptibility, importance to mission objectives, or exposure to the electromag- netic environment. The critical point is electrical in nature and nor- mally precedes the subsystem output stage. 197