Of a control element or a controlling system, the nature of the change of the output effected by the input.
Note:: The output may be a signal or the value of a manipulated variable. The input may be the control-loop feedback signal when the command is constant, an actuating signal, or the output of another control element. One use of control action is to effect compensation.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM