3. New calculation requirements

3.1 SIL reminder

The SIL (safety integrity level) specifies the integrity requirements for each safety function performed by E/E/EP systems. Four SIL levels ranging from 1 to 4 characterize these systems:

• SIL 4 refers to the "highest" safety level;

• SIL 1 refers to the "lowest" security level.

The concept of SIL applies to a RIS as a whole, and not to any individual component or sub-assembly. Nonetheless, some equipment suppliers are now using it as a selling point.

Standards IEC 61508 and 61511 define different...