SLI – Safely Limited Increment
The SLI safety subfunction prevents a movement from exceeding a specified increment. If the limit value of the increment is violated, the SLI safety subfunction will be triggered and a fault response will be initiated at the same time (usually STO).

| = | SLI safety subfunction monitored |
| = | SLI safety subfunction is triggered |
v | = | Speed |
s | = | Distance |
s1, s2 | = | Point at which SLI is activated. |
s2, s3 | = | Point at which SLI is deactivated. |
Δs | = | Safe increment |