Working on a couple of unit of Respironics Trilogy 202 and we are trying to use it for active ventilation with flow measurement. What we seem to notice is that the exhalation valve's diaphragm is not moving nor is there any air passing through the tubing for the exhalation valve. While using a simulator, we noticed that something like the air has to be delivered to the diaphragm during inspiration, that's the guess. There is a constant alarm for Check Circuit but there are no settings available as in the manual to change the circuit. Anyone have a solution for this?