Jim,
The Uniprom controller was mass produced by Montgomery so that they didn't have to make a bunch of job specific controllers with certain cards or card racks. Meaning - if your current job is a 2 stop Uniprom and the building wants to add 5 floors all you would do is add a couple cards. They wanted the controllers to be able to handle up to 7 floors I believe. Just so happens I'm sitting in front of one now.