Samsung iPOLiS SNC-570 User Manual page 40

Connecting Alarm Input
This is the input terminal for external alarm signal, use it by
connecting as following.
In case of selecting Normal Open at setup menu:
In case of contact type, it is short and in case of active type,
sensor input acts at "LOW" level.
In case of selecting Normal Close at setup menu:
In case of contact type, it is open and in case of active type,
sensor input acts at high impedance status(open collector).