It is an optical compressor pedal format. 4 knobs to adjust gain, level, compression and attack. The switch to trigger the effect is a bit light, but overall the pedal is in good order. Power is supplied by a 9V battery or a power supply type boss.
Not being familiar with compressors, I put a little time to understand the action of each volume pot. Especially since the effect does not include directly. I use this pedal to boost the clean sound of my Vox AC15, the settings are accurate and have a real impact on the sound.
The compression is very effective. It is discrete, does not distort the original signal too. Warning pedal blows when you push the compression to 3 / 4.
This pedal is perfect for my use. The effect is not spectacular but when it is bypassed, the lack is glaring. For that alone he deserves a good grade!