The Krohn-Hite Model 3940 programmable, dual channel, Butterworth/Bessel filter offers a programmable or benchtop filter covering a cutoff frequency range from 3Hz to 2MHz. It has a frequency response characteristic of maximally flat (Butterworth) for clean filtering in the frequency domain, or linear phase (Bessel) to provide pulse signal filtering. The passband gain is unity, and the attenuation slope is 24dB/octave per channel. The 3940 will accept input signals of ±4.5V peak and provides input and output gains of 0dB or 20dB which can be selected via the front panel keyboard or over the GPIB bus.
The filter can be programmed to operate in low-pass, high-pass, band-pass or band-reject modes, or the two channels can be interconnected to achieve 48dB/octave high-pass or low-pass slopes.
The Model 3940 offers to the user 99 groups of non-volatile memory for storage of front panel set-ups, which are stored in battery-backed CMOS. Set-ups can then be recalled with a simple command.
The 3940 also provides a self-test diagnostics upon power-up of its internal memory to insure the unit is operating properly. If a failure occurs, the display will indicate which ROM or RAM has failed.