BY a simplifying assumption we express amplitude, reaction, frequency, and change of plate current in triode oscillations in terms of the fraction of the time during which plate current is flowing. The mathematical methods are simple, and were used by E. V. Appleton and B. van der Pol, Phil. Mag., 43, 177, 1922.

A triode is an exhausted glass vessel containing three electrodes: a filament or heater, a grid, and a plate. Electrons emitted by the heater are caught on the grid and plate in numbers depending on their potentials, and constitute currents from the leading-in wires towards those electrodes, called the grid current and plate current. If Vgis the potential of the grid relative to the heater, and Vpthat of the plate, the plate current Ipis theoretically and experimentally a function f(Vp + μVg) of Vp + μVgover a large range, where μ is a constant called the amplification. Thus the curves of Ipfor different plate potentials Vpare obtained from each other by translation parallel to the axis of Vgby an amount proportional to the change of Vp. The grid current is much smaller if the grid potential is not too high.