The unavailable state means the connectivity or communications with the sensor is lost.
The PXE pings all managed sensors at regular intervals in seconds. If it does not detect a particular sensor for three consecutive scans, the unavailable state is displayed for that sensor.
When the communication with a contact closure sensor's processor is lost, all detectors (that is, all switches) connected to the same sensor package show the "unavailable" state.
Note: When the sensor is deemed unavailable, the existing sensor configuration remains unchanged. For example, the ID number assigned to the sensor remains associated with it.
The PXE continues to ping unavailable sensors, and moves out of the unavailable state after detecting the sensor for two consecutive scans.
Connected sensors always show unavailable if they are NOT under management.
For DPX2 or DX sensor packages, all of the connected sensor packages also enter the unavailable states if any of them is upgrading its sensor firmware.