This curve is one that is positioned using the clipper of the "INPUT" position. The curve, itself, is one with an increasing negative slope. The "OUTPUT" is blocked using the threshold of the "INPUT" until the threshold is reached.
In this case, the upper clipper of the "INPUT" is set at 100% and the lower clipper is set at 50%. The clipper window of the "INPUT" is used to drive the "Range Input" importance. The "Range Input" is used to drive the curve. The curve, itself, is created by driving the "Reverser" and the "Intermediate" positions. The "Intermediate" position provides an intermediate result. This provides a gradually increasing slope curve at the modified value of the "Intermediate" position. This curve is then inverted through "Reverser1" which is used to drive the supporting argument for the "OUTPUT".
"Reverser2" is used with the threshold of the "INPUT" position. This has the effect of blocking the "OUTPUT" until the threshold of the "INPUT" position is reached.