AJAX ReX Manual page 6

In order for detection and interfacing to occur, ReX must be located within radio
communication range of the hub (on the same guarded facility).
The request to connect to the hub is transmitted only when the device is
enabled. If the connection to the hub fails, turn off the extender by pressing the
power button for 3 seconds and retry the connection procedure after 5 seconds.
The extender connected to the hub will appear in the list of hub devices in the
application. The updating of device statuses in the list depends on the polling
time set in the hub settings; the default value is 36 seconds.
Choosing devices for operation via ReX
In order to assign a device to the extender:
1. Go to the ReX settings (Devices → ReX → Settings
2. Press Pair with device.
3. Choose the devices that should operate via the extender.
4. Go back to the ReX settings menu.
Once the connection is established, the selected devices will be marked with the
icon in the mobile application.
).