A food processing system 10 comprising a cooking apparatus 12 and a cooling apparatus 14. A difference circuit coupled to the differential pressure sensor has a difference output representing the sensed differential pressure minus a moving average. In one embodiment, the node can be disposed in a common local facility and connected to a common local area network with the at least one EIR terminal. An electrode supports a workpiece and generates a potential to attract charged particles from the process plasma toward the workpiece so that the charged particles strike the workpiece. In some embodiments the central computer can also transmit data, such as expected passenger lists, to the readers. The pen-based computer is operable to produce a human-audible output corresponding to the human viewable image contemporaneously with the interaction.