The following pneumatic mechanism and its electrical analogue :
As the control rod is moved up and down by an outside force, the distance between the plug
and the seat changes. This changes the amount of resistance experienced by the escaping air,
thus causing the pressure gauge to register varying amounts of pressure. There is little functional
difference between this mechanism and a baffle/nozzle mechanism. Both work on the principle of one
variable restriction and one fixed restriction (the orifice) “dividing” the pressure of the compressed
air source to some lesser value.