Stereo input and output, commonly used to control small signals, between the audio source and the preamp or between the preamp and the amplifier, string in the audio circuit to control the volume size. 3.5mm, RCA two kinds of interfaces, the internal use of Taiwan's high-quality with taps duplex potentiometer.Iso-response switch role: when playing music at low volume using frequency compensation network to properly enhance the and treble components to compensate for the human ear hearing defects, to achieve a better listening effect.Material: ABScolour: blackPackage Contents:1 x RegulatorOnly the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.