A system and method are provided for managing and prioritizing for action fleets of mobile robots deployed at various locations. The circuit arrangement also includes two duplexers which are connected in such a way that the two output signals emitted by the 90\xb0 hybrid that is connected to the transmission port constructively interfere on the antenna port, while spurious signals caused by the two output signals destructively interfere on the reception port. At least a peripheral portion of the air stream is exhausted from the shroud in a substantially laminar flow at an angle that is inclined from the vertical and is exhausted radially into ambient air as a substantially laminar air stream.