A filter is a circuit that separates some frequencies from others within mixed-frequency signals. It is used for preprocessing in measurement. The NF 3611 Multifunction Filter is a single channel multifunction active filter with variable cut-off frequency, which is used for signal analysis, rejection of unwanted components, separation of significant components, etc. in such fields as vibration analysis, acoustics, physics and medical science. The 3611 offers LPF, HPF, BPF, Band-elimination or THRU filter modes. The attenuation slope is 24dB/Oct and the Bandpass filter has 1/3 Oct bandwidths allowing simple frequency analysis to be made. The cut-off or center frequency can be set between 0.1Hz to 21.8kHz by means of 2 decade dials and a 5 step multiplier. In addition, the provision of gain and input-coupling switching permits the 3611 to be applied to still broader fields. The 3611 is your choice in filter selection.