The paper deals with a special class of feedback circuits in which the feedback path is closed at a discrete set of time instants that depend upon two arbitrary inputs

and

. Since the feedback signal is quantized in magnitude as well as in time, these circuits possess novel properties not found in ordinary linear feedback systems. The equations of such circuits are established and it is shown that these circuits may perform various mathematical operations, such as yielding inverse or reciprocal functions. Application to a communication method similar to delta modulation is described.