Theory of Automatic Control focuses on the theory of automatic control, including controllers, models, control processes, and analysis of systems. The book first offers information on the general introduction to automatic controllers and the construction of a linear model control system and the initial material for its analysis. Discussions focus on astatic controllers of indirect action, floating feedback, controllers of discontinuous action, static characteristics of elements and of systems, and frequency characteristics of a linear element and of the linear model of a system. The text then ponders on the stability of the linear model of an automatic control system and the construction and evaluation of the processes in the linear model of a system of automatic control. Topics include construction of the process from the transfer function of the system; construction of the control process from the frequency characteristics of the system; and analysis of systems with random disturbances given statistically. The publication takes a look at auto- and forced oscillation in non-linear systems, including approximate determination of forced oscillations in the presence of an external periodic action and determination of the auto-oscillations in the case of auto-resonance. The manuscript is a dependable reference for readers interested in the theory of automatic control.