I need to connect a few tstat 10s and some other bacnet mstp things in separate buildings and there are old telephones disconnected at the main NID on the entry pole but are still connected throughout the buildings underground. I wonder has anyone ever tried this? It is not twisted pair and not shielded so I don’t think it would work but maybe someone has done this? I’m going to try it anyway at a slow baud rate before I trench and bury conduit.
RS485 is a differential signal so this should work even if its a long way and affected by noise in the conduit. You could test the signal by hooking up a cheap oscilloscope, its a tool you should have around for any work with RS485 networking. The one below on the temco site is suitable but there’s cheaper ones on Amazon these days. Just make sure its a dual channel and can plot the A - B channel, the difference in the signal on the A and B pair of wires.
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