Monacor VNC-3052 User Manual page 66

If you select "N.O" on "Input sensor setting", when the switch contacts
are opened, the camera input alarm is triggered, and execute the
action user has set, for example, send a snapshot to E-mail address.
If you select "N.C" in "Input sensor setting", when the switch contacts are
closed, the camera input alarm is triggered, and execute the action user has
set, for example, send a snapshot to E-mail address.
c. I/O PIN definition
2. I/O Setup

GND (Ground): Initial state is LOW

DO (Digital Output): DC 5V

DI (Digital Input): Max. 50mA, DC 5V
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