I will do my best to include all info so there are not too many questions. I am working on a job with old tracer 100 controls. This includes about 360 comm 4 VAVs attached to 6 command modules which are attached to 3 tracer 100 panels (2 command modules per tracer panel). The info from tracer system is viewed via HyperTerminal front end. I made a list of all communicating vavs from HyperTerminal then removed comm 4 buss from command module and hooked up to JACE. When I perform a discover I am only seeing about a third of all the vavs on the buss that are shown communicating on HyperTerminal. Next I attempted to change the response timeout and intermessage delay and performed another discover. No change in VAVs discovered. I also did a trace while adjusting the response timeout/ intermessage delay and noticed that there is no change in discovery time when these setting are adjusted. In one case I turned response timeout up over 30 seconds yet I received a response timeout in trace utility within 2 seconds. I then noticed that only the newer UCM VAVs were coming through UCM 2, 3, and 4s. I then located one of the oldest boxes, that I confirmed was communicating and responding to commands via HyperTerminal, on the comm 4 buss and ran a direct connection between it and JACE. The JACE still will not discover it. I have talked with tech support in China several times and they are no help, keep saying it is a wiring issue. My question is simple what is the command module doing differently than the JACE as it can see all VAVs. I am also attaching a picture of one of the old style VAV boards in case this helps with troubleshooting. Any help is appreciated.