I was around at a customers' today - their Quartz 32x32 HD/RS422 Xenon router had stopped talking to it's control panels. Normally that is down to the coax 'QBus' cable that runs around all of the devices - like old-school 50ohm ethernet-over-coax - is prone to having a break in the middle or loosing a term from one end. However - this wasn't the case. A quick call to their tech support and you get an engineer who knows the products - can tell you what each board-LED means and what low-level commands you can send over the RS232 to illicit diagnostic information. In short order I re-loaded the configuration and the whole matrix was back up and running.