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Clientside and Towerside communicate over a UART link. We used to use a pair of XBee S3Bs but after we saw some reliability issues at SF5 we switched to using a pair of UART/Ethernet converters and running RLCS over the same long-range ethernet antennas that DAQ uses.
Safety
Since RLCS is responsible for handling the dangerous parts of launching the rocket, it must be extremely fail-safe and well-tested. Under no circumstances should there be any possibility of actuators changing state when there are personnel near the engine.
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