In this section we look at ways of using PID controllers in slightly more complicated arrangements than directly connecting the controller to the measurement and the manipulation. You should remember, however, that most PID controllers ARE simply connected - the special arrangements here are used in special cases (with the exception of cascade control which is used widely).
All of the control arrangements described here (other than cascade control) used to require extra 'boxes' to be bought and added to the control system. With modern computerised systems this is no longer the case and these systems can be configured with a few clicks of a mouse.