The output of "2" will always be less than the input at "1" by 0.35 bar (35 kPa), to prevent engine damage due to operation in the critical speed range.

A gradual rise of the input signal to "1" will cause a multiple stepped output from "2" proportional to the input signal.

The output signal from "2" will be equal to the setpoint of '17A' only when the input is less than the setpoint of '17B', permitting the transition signal to become modulated.

The output from "2" is equal to the input to "1" except when the input of "1" is between the setpoints of '17A' and '17B', when it will remain at the value of '17A'.