The NL125-6 Band Pass Filter is a module from Digitimer employs two active sections to control the high and low pass characteristics. The low-frequency cutoff point can be set continuously from 0.5Hz to 5kHz with a single turn potentiometer, in four switched ranges.

Similarly, the high-frequency cutoff of this notch filter can be set continuously from 5Hz to 50kHz in four switched ranges. DC and WB (wide band) switch positions by-pass the lower and upper filter sections, respectively. A switchable active band-pass filter is provided for the rejection of line frequency interference; this can be set by the user to 50Hz or 60Hz, with a 20Hz notch width (-3dB points).