I tried to install another dust monitor at end X to be placed inside the receiving bay. I connected two 25 ft. DB9 serial cables together and connected the dust monitor labelled 'U' to the unused port on one of the break out boxes. The other port is used by the dust monitor at location 1. However, this caused both dust monitors to return garbage characters. I tried turning off and disconnecting the serial line (at the breakout box) for the dust monitor at location 1, but the new dust monitor continued to return garbage. I removed the new dust monitor and reconnected the one at location 1, but moved it so it could be easily placed on the other side of the roll up door and inside the receiving bay. This is back to the original configuration and communicating correctly.

I had to restart the IOC for the dust monitors at end Y, after the Comtrol serial to Ethernet box momentarily lost power.