The RSA 1.0 is a RS232 "translator" or something like that. It is a little black box that sits between your control system and the MZC device. I have read of people trying to bypass it and control the MZC directly with a RS232 cable, but there are some things going on there that prohibit it from being so easy apparently.

The RSA 1.0 seems to be a unicorn item to find. Ebay might turn something up now and then. Or chances are there are some old SC dealers that have some collecting dust in the warehouse. LOL

I am surprised there are still working MZC units out there. We replaced so many amplifier modules in those things. If I ever run across one, my first recommendation will be to dump it in the trash and replace it.