HIKVISION DS-2CD2412F-I Quick Operation Manual page 18

Network Camera·Quick Operation Guide
Figure 4-2 Searching Online Devices
Device can be searched and displayed in the list in 15
seconds after it goes online; it will be removed from the list
in 45 seconds after it goes offline.
Search online devices manually:
You can also click to refresh the online device
list manually. The newly searched devices will be added to
the list.
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