Hardware is a Tracer 100l that has about 25 or so TUC's and two UPCM's. I have a Comm4 driver and a JACE (FX60) with a Aux comm card setup. I cannot discover any devices. The discover bar works but no devices discovered. I am sure it is a setup issue. The Tracer connection thru HyperTerminal or equivalent was 2400. What does the Comm4 trunk communicate at? The Tracer was installed in 2000 and has a comm4 card. I installed it back then. Of course the Trane comm trunk is 2 wire and JACE is a tree wire RS485.I can only guess at the wiring. I am no longer working with Trane and trying to remember to much these days. Any assistance is appreciated.