EUCHNER CETx-AP-xxx-AH-xxx (Unicode) - Manual (Page 7)

Operating Instructions Safety Switch CET.-AP-...-AH-...
7
The system is designed so that failures will not result in the loss of the safety func-
tion. The occurrence of failures is detected by cyclic self-monitoring at the latest
on the next demand to close the safety contacts (e.g. on starting).