BOSS RCL-10 Compressor/Limiter
A Compressor/Limiter automatically applies volume reduction. It squashes your input, ie. reduces the loudest parts so the overall volume level is more even. This can have many benefits, eg. smoothing out a vocal or acoustic instrument performance which has large volume fluctuations; making drums more punchy; or making electric guitar have more sustain.
This box includes a noise gate, if you have problems with noise in your signal this can help reduce it.
Compressor/Limiter/Expander section: Threshold (sets how loud the signal has to get before the volume reduction effect kicks in), Ratio (basically the strength of the volume reduction effect), Attack (how quickly the volume reduction starts), Release (how quickly the volume reduction goes away).
Noise Gate section: Threshold, Decay.
Plus there's an Output level control.
Powered by 9V DC centre-negative power supply.