According to its Data Sheet, the Flexidome IP 3000i IR camera has 2 options to activate the alarm input.
Please refer to the diagram below if you would like to get alarm input from some physical sensors.
Connect Alarm Input / Output Port:
It needs to increase pull-up resistance externally to work normally. After external pull-up resistance is increased, the default output signal is high level (external pull-up voltage), and it switches to low level when there is alarm output.