Solution of Linear Differential Equations with Variable Coefficients by the Electronic Differential Analyzer

A relay device is described which varies resistance in a stepwise continuous manner in order to approximate arbitrary functions of time. The device can be used with electronic differential analyzers to solve linear differential equations with variable coefficients. Sample solutions of Bessel's equation are included as examples. Calibration and measurement techniques which permit computer accuracies, of several hundredths of a percent are discussed.