The outflow Valve is a small door that opens and closes by a computed Automated demand or manually by a switch in the flight deck.
Three motors can drive the door open by its respected computer/controller or swich, but only one can be in command at any one time, generally x2 AC motors for Auto 1 or Auto 2 operation and a DC Motor for manual operation.
The contoller/computer works to a schedule derived by the outside ambient px to the inside cabin px and this rate of px/flow commands the valve to open or close, usually to a 500ftperminute climb or descent.
In cruise the valve is open slightly to allow a flow of air through the cabin, regulations stipulate each passenger must recieve xlbs/hr.
The flight crew report to engineers if the valve is closed more than a given percentage as this tells us the aircraft has a possible leak of air from other than the ouflow valve.
Hope this helps
Beeline