Outflow Valve
There are 2 outflow valves each controlled by a CPC. Each outflow valve also has a 3rd motor (in addition to the 2 from the CPC) to allow manual control. In manual mode, the outflow valves move at 1/5 the speed of automatic mode.
During the takeoff roll, the outflow valves are slightly closed to pre-pressurise the aircraft (about 0.1 PSI).
With the valves in automatic mode, they close at 15,000' cabin altitude, independently of the CPCs and other valves.