Since you used the terms AUTO 1 and AUTO 2, I am going to ass-u-me that you are using the B757/B767 aircraft as your model for study.
The B757 uses to Digital Cabin Pressure Controllers, Auto 1 and Auto 2. The Outflow Valve has 3 motors on it:
One controlled by Auto 1
One controlled by Auto 2
One controlled Manually by the flight crew using overhead panel
The Cabin pressure controllers automatically control cabin pressure based on Current altitude, the planned Altitude (Cruise or Landing field altitude) and the actual cabin pressure.
The B757, unlike the B737 series (and I belive the MD80) DOES NOT have automatic switching during air/ground mode transition. So the first crew of the day usually chooses which controller will start in control for the first flight of the day using a very complicated formula. On Odd nunbered days, Auto 1 will start in control and be switched by the flightcrew on each subsequent flight. On even numbered days, Auto 2 will start in control.
The controller not in command, will remain in standby waiting for a failure of the controller in command. If a failure shall occur, then control will switch automatically.
If both controller fail, then the crew can manually control the outflow valve to maintain cabin pressure.
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Furthermore, why is the Cabin ROC controlled in the manual mode?
The Rate of Climb is not controlled by the ROC knob in manual mode. The knob is for setting the ROC in Auto Mode.
And finally, I`m not quiet sure if I got the point about the landing elevation selector.
Setting the Landing Elevation allows the Auto controllers to schedule cabin pressure for descent and landing.
Is it right, that the system increases the pressure during decent until reaching this predetermined value?
Huh?? Cabin Differential Pressure & Cabin Altitudes should decrease with descent.