For automatic throttling control a valve positioner is required.

The positioner accepts a 3 - 15 psig. or 6 - 30 psig. variable signal from a control instrument or D/P cell and positions the valve in its stroke to maintain a constant and stable condition of pressure or flow in accordance with a varying demand or load.

For information on Electro-pneumatic positioners to accept a milli-amp signal and convert it to a pneumatic signal contact the factory or your nearest sales representative.