A sub-audio time delay circuit

Through the use of an electronic differential analyzer arranged to give a sixth-order approximation of the Laplace shift operator, it is possible to reproduce an input signal and delay it T seconds when the highest angular frequency present in the input signal does not exceed 12/T. Inaccuracy due to nonlinear phase shift is less than 2% under these conditions. This device requires only linear computing elements, and will permit delays of seconds within a finite frequency spectrum. An application to a closed loop industrial control problem is cited and other applications are suggested.