How to trigger warnings on an unplugged aural warning unit?
Answering my own question based on tips posted on comments:

As @Gerry suggested on comments, they are OPEN/GROUND, if i ground any of sensor cables it'll trigger the alarms. Those lines are 5V, and i think that most of sensors are just simple switches, except for the Fire Alarms, that i  couldn't trigger and has 6.8V over its line.

For now i got my AWU speaking.

Thank everybody who commented with their suggestions. Those were very very very useful,  you guys are awesome!