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Answer: You shouldn't have any issues with beltpacks logging onto the inside antennas if you are using a 1.9 GHz system, up to five beltpacks can log onto a single antenna so with 3 antennas up to 15 beltpacks should be able to log on to the inside antennas. If you have issues with all the BPs logging on it might be useful to add an additional antenna to the inside coverage pattern so that you have some additional room to roam as it is a good idea to have additional slots open on antennas so that BPs can jump from one antenna to another depending on where they are in the coverage pattern.
There is no timeout for FSII beltpacks logged onto a particular transceiver antenna, they can stay on a specific antenna indefinitely until the beltpack wanders out of its range, the RF link quality is too low or the BP powers down.