Effect is made for mixing dry and processed signals.
In mixing mode (LED is lit) dry signal from input is mixed into processed signal. Levels of dry and processed signals are set by DRY and WET knobs.
In "pass through" mode (LED is not lit) effect works as LineSel in same mode.
(OUT) <= [RainSel] <= [FX2] <= [FX1] <= (IN)
When ON: OUT = IN x DRY + FX(IN) x WET
When OFF: OUT = IN