Festo CTEU-CO Manual, Functions And Maintenance page 50

2. Diagnosis
2-14
Then the master controller is monitored based on monitoring
of activation with the configured monitoring time (see DS 301).
When monitoring is activated, the configured emergency stop
response (Fault reaction option code object 605Eh, PNU
1021) is executed and the drive is stopped.
Select the "Guard Time" with reference to the dynamics of the
system.
Refer to your master controller documentation for details on
how to activate Node guarding.
Festo P.BE-CTEU-CO-OP+MAINT-EN en 1101NH