@bigkid posted:I seem to recall base3 can get messages back via the tracks (over the ground side I would assume) from a suitably equipped engine but that is the only 'active' thing on the track side.
I can see no way the BASE3 is sending return traffic on the tracks. I'll bet money and give you odds that they're using the Bluetooth for the return traffic. The TMCC/Legacy carrier is continuous on the rails, and it's a unidirectional signal. Also, if they attempted to have the locomotives send return traffic on the rails, they'd have all the issues that DCS has with two-way traffic on the rails. Since any new locomotives and the BASE3 are being fitted with much longer range Bluetooth hardware, that would be the logical and painless way to send the return signal.
I could conceivably be wrong, but based on considerable experience in the field, my money is on the BT link.