Alarm overide wire, help!!

Ive purchased an aftermarket alarm and want to fit it inconjuction with my factory alarm system. I have a NATS2 system (Nissan Anti-Theft System mark 2) and was wondering if any if you guys have a clue if they are the same as the G20 factory alarm, and if so, is there a wire on the alarm that i can attach this (-) negative output from the new alarm to the factory alarm to overide it?