Parameter assignment for this function block is accomplished by selecting the GAIN of the derivative unit and the lag time constant LAG by which the output OUT will be delayed.

For very small sample times and the unit jump to the IN input (jump in at IN input from 0 to 1.0), the OUT output jumps to the GAIN value (theoretical value - actual slightly smaller due to the not infinitely small sample times), in order to return the LAG time constant to 0.