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Calculations have been made of the collective field emission and thermally enhanced emission from a multiplicity of emitters in order to simulate the properties of large-area electrodes in vacuum subjected to high voltages. The individual emitters were assumed to be noninteracting. In one set of calculations, the individual emitters comprising the groups were characterized by randomly selected values of β, work function, and projection height lying between the limits of 50 and 200, 4.4 to 5.0 eV, and 0.5×10−4 and 10−3 cm respectively. In other computations values of work function and projection height were fixed at 4.5 eV and 5×10−4 cm respectively and values of β determined from an assumed normal distribution with a central value of 100. It is the intent of this work to show the behavior of these collections of emitters in detail. Although the collective emission from these groups yielded an apparently straight-line Fowler-Nordheim plot, computed values of effective β and effective emitting area varied noticably with field. At low field the effective β is closely similar to the maximum value of β in any given collection of emitters. As the field is increased, the effective β declines while effective emitting area increases. The change in effective β over an average field ranging from 100 to 500 kV/cm is typically 5%–10%.