You can tell when a slave SyncBac PRO is connected with a master by looking at its main screen display.
An antenna icon flashes in the top-right corner when the slave and master are communicating. The number shown to the right of the antenna icon shows the signal strength (0-7 where 7 is the maximum signal strength).
Note: The LED flashes green in time with the master when a connection is established and maintained. The LED flashes blue if it has lost its connection to the master.