The Krohn-Hite 3700R Variable Band Pass Filter has attenuation slopes of 24 dB per octave, with upper and lower cutoff frequencies independently adjustable from 0.2 Hz to 20 kHz.
Maximum attenuation of 80 dB. The frequency response characteristics is a fourth-order Butterworth with MAXimal FLATness for cleanest filtering in the frequency domain. Rack mounting version.