Inputs/Outputs (I/O’s)
The digital I/Os on, for example, a network camera can be used to connect any device that can toggle between an open and a closed circuit. 

If, for example, a door switch is used as an input device, opening the door could trigger the upload of video images and the sending of notification messages. 
An output might, for example, be used to automatically start a siren when there is a motion detection trigger.