OK. I still don't get it. The crew still must ensure that they do not fly below the min IFR altiitude but the ADRU will correct for cold temperature errors of the aircraft's altimeter. Let's say that the crew chooses to fly at the min IFR altitude (let us assume that the published min IFR altitude is 3700 feet). The crew descends to 3700 indicated on the altimeter but that is OK because the ADRU compensates for the the cold temperature error and the procedure designed obstacle clearance is not violated. What happens if the crew chooses to fly at 4000 feet? Is that atitude compensated for cold temperature by the ADRU and if it is that aircraft is not at the same atitude as other aircraft without compensation at 4000 feet! At what point does the ADRU not affect the altimeter reading in the cockpit due to temperature (below or above ISA)???