A breathing apparatus is operable in self-contained and filtered modes of operation. A primary operating system runs on a processor or uses a particular display. This exemplary embodiment comprises input logic that includes one or more memory-input paths coupled to respective memory inputs of the embedded memory, a memory built-in self-test controller, and at least one scan cell coupled between the input logic and the MBIST controller. The shape of the article material may be adjusted to concentrate the stress so that the damage initiates under the sensor. The coarse shifting in the delay line at high clock frequencies does not affect the phase relationship between the intermediate clocks fed into the phase mixer.