Siemens SIRIUS 3SK1, Manual, Page: 35 / 262

Safety systems - General information
4.3 Basic terminology
3SK1 safety relays
Manual, 04/2013, A5E02526190021A/RS-AA/01
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4.3.9 Monitored start
For a monitored start, the device is started by operating the START button, but only after the
input image has been checked and a positive test of the safety relay has been conducted.
Contrary to the manual start, the monitored start evaluates a signal change of the START
button. This means that the START button cannot be bypassed (misuse). For PL e (ISO
13849-1) as well as SIL 3 (IEC 62061), the monitored start must be used in the case of
EMERGENCY STOP. For other safety sensors/functions, the necessity for a monitored start
command depends on the risk assesment.
If the START button is operated for more than 2 seconds, the 3SK1 basic unit detects a
wiring short-circuit in the START button and switches to the fault state (Device = green; SF =
flashing red; Out = flashing yellow; IN = off)
Note
In the delivery state of the 3SK1 safety relays, the start type is set to "Monitored start".
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Figure 4-4 Start function "Monitored start"