A patient interface support that supports a patient interface of a PAP device and generates a pre-selected engagement pressure at the patient interface to create a seal between the patient interface and the patient’s airflow passages when the interface support is in use while alleviating the strain on the patient’s head. Workpiece feature quality is predicted based on decomposition of the machining process into sources of variation, reticulation of the machining process into machining stations and error models that account for significant contributions to feature quality including from categorical sources of variation. Authentication of the user is based on both a match score indicating how closely the captured voice samples match to previously stored voice samples of the user and a pass or fail response indicating whether the voice sample is an accurate reproduction of the word string. The current divider can generate a divided current by dividing an input current by an adjustable division ratio. A registering unit registers, at each of the first reference points, the fourth color data set that is set in correspondence with the single fifth color data sets.