SABINE FBX-900 is an automatic feedback controller that utilizes nine independent digital notch filters to eliminate acoustic feedback in sound systems. It can be placed anywhere in the sound system that a graphic equalizer might be used, but the most common place is between the output of a mixer and the input of a power amp. The FBX-900 has two types of filters: FIXED and DYNAMIC. FIXED FILTERS retain their frequency center-points until the unit is reset by the user, while DYNAMIC FILTERS control intermittent feedback that comes and goes throughout the program.