wire up battery back-up siren

 So i have a crimestopper fm RS/Alarm.I was thinking of adding a battery backup DEI siren,but also leave the other one connected.I only want the DEI one to work on door open or hood up .So i was looking though my manual it has the optional horn honk(which is not connected because the horn on my colorado sounds very weak)but in the programming options it saysFACTORY HORN CHIRPS CAN SET JUST FOR DOOR AND HOOD ONLY.Does that mean during alarm trigger?And can i set up the DEI siren though relay of negitive pulses to provide constent negitive to ativate this siren when triggered by the door or hood opened only or when battery is cut.How should i wire it ,it is the 3 wire POS NEG TRIGGER.And thanks for all the help and knowledge this site gives.colorado tap the rockies