When the pressure increases in Bourdon tube 1, shutter 2 approaches nozzle 3 and the pressure before the nozzle is raised. This pressure acts on a valve which releases air from a servomotor, thereby reducing the pressure acting on membrane 4. At this, nozzle 3 is withdrawn from shutter 2. When the pressure drops in the item being controlled, the elements of the regulator operate in the reverse direction.
$3912$LHP,Rg$