Rare item. Compressor limiter with control knobs for adjusting sound quality. - Brand: Carl Martin - Model Name: Compressor Limiter - Control Knobs: TRES, COMP, RESP, GAIN - Connectors: OUTPUT, INPUT - Switch: ON/OFF - Country of Manufacture: Denmark Used only at home. There are some scratches on the back, so I've marked it as "Slightly scratched or dirty." Please consider this a used item and understand before purchasing.