Siemens SITRANS DA400 Operating Instructions Manual page 50

Evaluating and processing signals
7.4 Acknowledgement
¬St.Ac
Figure 7-7 Acknowledgement evaluation
7-10
Not stored but can be acknowledged
Time 1: Alarm value exceeded, alarm is output.
Time 2: Acknowledgement with <ACK> key, alarm is reset.
Time 3: Alarm is only set if the alarm value is exceeded again.
Time 4: Value below alarm value and alarm canceled.
SITRANS DA400 with protection against explosion
Operating Instructions, 02/2006, A5E00684661-01