The paper discusses a technique for improving the response of a saturating servo mechanism subjected to random signals. It is shown that a non-linear error detector gives a considerable reduction in error magnitude for a large range of input signals. It is possible to design the additional non-linearity to optimize the performance of the system for all input magnitudes. This form of non-linearity has previously been shown to effect improvement in the response of such systems to step-function and sinusoidal inputs.Experimental work verifies the predicted results for a particular system, and shows that considerable latitude is permitted for the characteristic of the additional non-linearity.