For stepless(infinitely variable)capacity control of air compressors:Suction control valves,bypass valves,bleed valves and engine speed controllers are govermed by the signal from the proportional controller.
Controllers LP5E are positive acting.Within the control band(see diagram)they give a proportionally rising singal at A on increasing pressure at E.
The set point is adjusted by turning the hand wheel
* to a higher pressure: clockwise
* to a lower pressure: counterclockwise