Every alarm system is different. That's one reason you should not mix equipment from different manufacturers, or even product lines.
In general, a burglar alarm is designed so that any fault causes a contact to close in the panel. As mentioned, this is usually be having a NO contact held closed; open it, or cut the wire, and the alarm sounds.
Fire alarms are a bit different. they often operate in both modes; one for "alarm," and one for "let's make sure the line is working." Resistors, diodes, DC power are all part of the picture.
In short, there is no simple answer. Alarms are but control circuits ... so any combination is possible.
