Compact optical compressing effect pedal that performs gain reduction control via a light source into a photo sensitive cell – as the light source gets brighter, the photo sensitive cell sends a signal to reduce dynamic range, or what becomes a compressed signal. The four controls (from left to right) are the Gain, which controls the ‘pre-glow’ of the optical circuit; Level, which controls the overall volume of the compressor; Compression, which controls how hard or soft the compression is, and the Attack control which takes the signal from transparent to outright total squeeze. It comes in a solid die-cast housing with cool chicken-head knobs, CM colour and graphics and a 9V battery compartment. Due to the nature of compressors, it is highly recommended to use a regulated power supply (like the CM ProPower).