Abstract: The response characteristics of an electronic filter are automatically adjusted as a function of the magnitude of an applied DC voltage to permit the same filter to be used for varying applications. Embodiments for varying the center frequency and Q of the filter are disclosed. The filter has particular utility in vibration monitoring systems wherein the center frequency may be selectively set at a value which is characteristic of the frequency of particular vibration signals of interest. In a disclosed vibration monitoring system incorporating the voltage controlled filter of this invention, which is particularly useful for monitoring vibration levels in gas turbine engines, the magnitude of the DC control voltage is varied as a function of gas turbine rotational velocity.