What characteristic defines supervised devices in an alarm system?

Supervised devices in an alarm system are defined by their ability to regularly communicate with the control panel. This characteristic is essential because it ensures that the system can continuously monitor the operational status of each device. Through consistent communication, the control panel receives updates about the devices' functionality and can detect any failures or malfunctions immediately.

This proactive monitoring helps maintain the integrity of the alarm system, allowing for quicker responses to issues such as battery failures, tampering, or disconnection. If a supervised device stops communicating for any reason, the control panel can trigger alerts or notifications, thereby enhancing the overall reliability and effectiveness of the alarm system.

The other answer choices do not accurately describe supervised devices. For instance, operating autonomously without connection contradicts the very essence of supervision, which requires active communication. Being used only for emergency notifications is too narrow, as supervised devices often perform multiple functions beyond just emergency alerts. Lastly, requiring manual check-ups does not align with the purpose of supervision, which aims to automate monitoring and reduce the need for such interventions.