The new Gold Line Model FD-23, used with any equalizer, is the fastest and most effective way to eliminate feedback. The FD-23 makes use of the same filters used in expensive 1/3 octave analyzers. You can simply and quickly RING-OUT any room by raising the level of the sound system until feedback occurs. The LED display of the FD-23 will indicate which frequency to CUT allowing the minimum cut necessary to keep the music while eliminating the feedback. The FD-23 is a rugged portable instrument with built-in microphone and is powered by AA batteries or a 12 volt DC supply. Dimensions: 31/4"W, 8"L, 21/4"D. Weight: 12 oz.