When the EN input of a function block goes low Unity is designed to zero-out the outputs of blocks where links are attached, or maintain the last value if a variable is attached. Former users of Concept will be accustomed to the outputs remaining at their last state irrespective of whether a link or a variable is attached to the output.
NOTE: There is a a Project Setting in Unity which will maintain the output state of an EF when EN goes low. By default this setting is not selected.
To maintain the output state of a disabled EF go to Tools/Project Settings/Program/Language Common. Select "Maintain Output Links on Disabled EF or EN=0"
Selecting this option will negate the manner of operation described in this FAQ.