The type of monitoring solution you choose should be determined by the level of back up you require. Digital monitoring is fine for most but would fail should the phoneline fault or be cut. DualCom offers a dual signalling system so that it will still notify the response centre should the line be tampered with. BT RedCare is the most secure monitoring system as it continuously monitors the alarm and would be able to detect any issues with the line, even if the alarm itself was not triggered.
When alerted to the alarm being triggered the alarm response centre would perform checks to confirm the alarm, notify the key holder and, if appropriate, alert the police.