Abstract: A circuit (10) receives a cyclic input signal having a frequency determined by a source (11), which frequency may vary in accordance with a parameter or condition to be measured, for example. The circuit (10) very precisely provides an output current representative of the frequency of the input signal. In particular, the circuit uses a pair of regulated and different voltage (16)(17), one (16) of which is impressed upon an averaging circuit (30) for a preselected time during each cycle of the input signal, and the other voltage (17) is impressed upon the averaging circuit (30) during the time when the first signal is not connected to the averaging circuit. A control signal (V.sub.o) is developed from the averaging circuit (30) which is a function of the average of the voltage provided to the averaging circuit, and the control signal (V.sub.