Which monthly tolerance category applies to interlock-related tests such as gating interlock?

• A. 1%
• B. 2%
• C. ±1 mm
• D. Functional

Answer: (D)

Interlock-related tests focus on whether the safety function works as intended, not on measuring a physical dimension. For monthly checks of things like a gating interlock, the key is whether the interlock actually prevents or allows operation correctly under specified conditions. That kind of assessment is binary: the interlock functions or it doesn’t. Because the criterion is functional performance rather than a numeric measurement, the functional category is the appropriate monthly tolerance. The other options represent quantitative measurements (percent or a distance) and don’t apply to validating a safety function.