A.24. The hardware items necessary to perform the functions mentioned in this Safety Guide belong essentially to instrumentation systems for safety related information and protection systems. However, this hardware may be partially shared with other systems of a higher safety category. In this case, the higher safety category should be adopted for the common part, and the remaining hardware should not unacceptably reduce the reliability of instru­mentation systems classified in the higher category. Reference [17] should be used to establish the importance to safety of, and the appropriate design recom­mendations for, the monitoring instrumentation. These recommendations should cover:

— Failure rate analysis;

— Environmental qualification;

— Quality assurance;

— Checking, testing and calibration;

— In-service inspection.