Three-band stereo equalizer for expanded frequency response and acoustical contouring. Ideal for portable audio use including laptops, MP3, DAT and CD players. The EQ50 is pocket size for easy travel and portability. There are level controls on the EQ50 for bass, midrange and treble which provide added sound definition. Unity gain amplifier limits power from the source. Operates on (2) "AAA" batteries (not included) for 15-20 hours of use.