What is the correct option for a sensor that is already installed in the Control Panel?

The term "existing" accurately describes a sensor that is already installed in the Control Panel. This terminology implies that the sensor is currently present and operational within the system. Understanding the context of system components is crucial, especially when configuring or managing security systems.

Using "new" would incorrectly suggest that the sensor is recently added or unused, which does not apply to a sensor that is already part of the setup. The option "refurbished" could imply that the sensor has been restored to a working condition after being previously used, which is not relevant here since the focus is on its current status in the Control Panel rather than its history. Lastly, "inactive" would mean that the sensor is not functioning or not currently in use, which contradicts the idea that it is already installed and presumably active within the system. Therefore, "existing" is the most appropriate term to describe the status of the sensor in this context.