Dynamic range compression is designed to help the audio engineer to manage the dynamic range of audio signals. Prior to the invention of automatic compressors, audio engineers accomplished the same goal by "riding the faders", listening carefully to the mix and lowering the faders of any singer or instrument which was getting too loud. A compressor accomplishes this by reducing the gain of a signal that is above a defined level (the threshold) by a defined amount determined by the ratio setting. Most compressors available are designed to allow the operator to select a ratio within a range typically between 1:1 and 20:1, with some allowing settings of up to ∞:1. A compressor with high compression ratio is typically referred to as a limiter. The speed that the compressor adjusts the gain of the signal (attack and release) is typically adjustable as is the final output or "make-up gain" of the device.