An air delivery system includes a controllable flow generator, a primary controller, and an auxiliary controller. The flow generator is operable to generate a supply of pressurized breathable gas to be provided to a patient for treatment. The primary controller is associated with at least one primary control feature to select at least a first aspect of operation of the flow generator. The auxiliary controller is associated with at least one auxiliary control feature to select at least a second aspect of operation of the flow generator. The second aspect selected by the auxiliary controller is different than the first aspect selected by the primary controller. The primary and auxiliary controllers may be interchangeably usable to control operation of the flow generator.