A:Answer No, no siren would go off. However, the system does communicate to ADT monitoring when the alarm is initially tripped, and again when the correct code is entered to disarm (sends a CANCEL signal to ADT). So, if the second signal to disarm is never received, ADT monitoring will call you and then dispatch police if you don't tell them it's all clear. In this way, I believe, even if the intruder quickly smashed in the control unit, it'd be too late as ADT would already be counting down for the disarm code.
