Thank you for clarifying @rhysowen! In this specific scenario, where there is no network connection and no cellular backup due to not being subscribed, your Alarm Base Station will lose connection. As it does not have a form of communication available, your armed mode will not change, nor will siren sound. Once connection is restored, the Alarm system will reconnect and should return to it’s last known mode.
If you are concerned about specialized burglars or a scenario such as this one, we recommend adding Cameras to your “Ring of security”. This will help to cover the outside of your home as well as the inside! 