In older devices, the unstable interval counter is reset to zero.

• A. True
• B. False
• C. Not applicable
• D. It depends

Answer: (A)

The idea being tested is how older device logic handles irregular rhythm signals during tachyarrhythmia detection. In those older systems, there is a counter that tracks unstable or irregular intervals. When the intervals become non-stable or out of the expected pattern, that counter is reset to zero to start fresh. This reset prevents past irregular beats from influencing future detections and makes sure a new sequence of consistently short intervals is needed before a tachyarrhythmia message is triggered. In short, irregularity clears the counter so detection requires a new, stable sequence, which is why the statement is true. If intervals remain consistently short, the counter can build toward a detection threshold; if instability recurs, it resets again.