I don’t know anything about American District Telegraph fire alarm panels, I’d assume it’s similar to the FireLite ones, but I’m not sure about its software or if it has a backdoor.
I’d recommend taking a look at this topic: <URL url="So you want to buy a FACP... text=“viewtopic.php?f=60&t=6110”>So you want to buy a FACP...
My guess is the FireLite version would be a safer buy than the ADT one on the software side, but someone who has experience please correct me.