How Does a Control Valve on Back Cascade Mode Operate?

If a control valve is put in auto mode it tracks the set point given to it by which i mean it opens or closes depending on weather the present valve goes above or below the set point that we give to it

If a control valve is put on manual mode we fix the opening and there is a fixed flow through the opening if we want more flow we open the control valve more and vice versa

In a cascade control the control valve maintains the set point by controlling two other variables. For example The furnace coil outlet temperature control valve is cascaded with either the oil flow control valve or the gas flow control valve so it maintains the coil outlet temperature by varying either the gas flow or the oil flow through the furnace depending upon the one it is cascaded with

how does a control valve in back cascade mode work ? Can anyone explain it with an example?

whatever that i have given above is just my understanding if it is wrong kindly correct me