The 2231 graphic equalizer shall be a mono 31-band type with frequency centers on standard ISO 1/3 octave frequencies ranging from 20Hz to 20kHz. The boost/cut range shall be switchable via a recessed front panel switch to either +/-6dB or +/-15dB and the selected range shall be indicated on the front panel by either of two LEDs. Low-noise equalization sliders having a 45mm travel shall be utilized having center detents at 0dB. The equalizer shall have a front panel 41-detent rotary input gain control having a +/-15dB range. Bypassing the equalizer section of the signal path shall be accomplished via a front-panel switch having a corresponding LED to indicate when it is bypassed. A 40Hz low-cut Bessel filter with 18dB/octave slope shall be insertable in the signal path via a front panel recessed switch and shall have an LED to indicate when the filter is active. The graphic equalizer shall incorporate dbx Type III™ Noise Reduction providing up to 20dB of broadband noise reduction, having a front panel switch to enable the noise reduction and an LED to indicate when it is active. The equalizer shall also be equipped with a dbx PeakPlus limiter system. Electronically balanced/unbalanced inputs shall include 1/4" TRS, female XLR, and screw terminal barrier strip, while servo-balanced/unbalanced outputs shall include 1/4" TRS, male XLR, and screw terminal barrier strip shared with the input.