Four methods for the analysis of time-variable circuits

THE GENERAL theory of electric circuits whose component parameters are linear and constant has been extensively developed and is well understood. In recent years, considerable attention and effort has been directed to the analysis and performance of circuits whose parameters vary with the time. Many of the most important and interesting problems of circuit theory involve variable. parameters. For example, the equivalent circuits of the microphone transmitter, the condenser microphone, the induction generator, the superregenerator and of many other practical devices contain parameters that are time-varying. Many systems in mechanical and acoustical engineering in which the compliance or the inertia parameters vary with the time lead to the same mathematical formulation of their behavior as do the time-varying circuit problems.