The Switch block passes through the first input or the third input based on the value of the second input. The first and third inputs are called data inputs. The second input is called the control input. Specify the condition under which the block passes the first input by using the Criteria for passing first input and Threshold parameters.
So in context, if the clock2 is >= 20 then the constant is passed, and if clock2 < 20 then the output limited pu1 is passed.
