Crossovers may do nothing more than direct frequencies, but the thought that went into the 223 and 234 is what really elevates the dbx® crossovers above the rest. The 223 and 234 both feature differentially balanced TRS 1/4" inputs and outputs.To prevent accidental changes of critical settings during performance (which could be disastrous), several of the 223 and 234’s controls are located on their rear panels. On the 223, the first of these selects between stereo two-way or mono three-way operation, while on the 234 it selects between stereo two-way, stereo three-way, or mono fourway operation (the selected mode is always visible via two green front panel LEDs). Also located on the back panels are switches that allow you to individually select crossover frequency ranges for both channels (again, the front panels feature green LEDs to indicate when the back panel x10 switch is activated). The rear panels also allow you to mono-sum the low frequency outs. Both crossovers feature Linkwitz- Riley 24dB/octave filters–the professional standard. Each of the units’ channels has a +12dB input gain control and a recessed 40 Hz low-cut, high-pass filter for removing low frequency rumble. Both the low and high outputs on each channel have phase reverse switches (reconfigurable to operate as mute switches) and gain controls ranging from ° to +6 dB, allowing level matching and muting of individual outputs.The 223 and 234 give you great performance, the features you expect from professional crossovers, and the reassurance that you’re buying from the company that has been making the world's finest audio gear for over 30 years.