The Input control sets the input signal level to the compressor, which, in the 1176 design, determines both the threshold and amount of peak reduction.
The Output control sets output level. Use it to bring the signal back to unity after applying gain reduction.
The Attack and Release controls set the attack and release times of the compressor. Full counterclockwise is slowest, and full clockwise is fastest. Attack times vary between 0.4 milliseconds to 5.7 milliseconds. Release times vary between 0.06 and 1.1 seconds.