Siemens SIMOCODE pro Manual page 25

Mounting and connection
4.2 Mounting
Figure 4-2 Mounting on a standard rail (2)
The terminal blocks can be removed in the order a, b and mounted in the order c, d.
SIMOCODE pro - Fail-Safe Digital Modules
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Manual, 11/2017, NEB631679702000/RS-AA/002