It is interesting where this conversation turned. But for history's sake... NAC started on PM2e with Microcom's, and then USR Sportster. I remember USR sending us PROM chips to change from 28.8 to 33.6. After that, PM3's. We were early PM3 users, working with Megazone on an almost continuous basis to work on bugs. We tried the PM4, that went nowhere. Then we tried Assured Access - it had promise but ultimately was no good. Ultimately, went to used AS5800's with ChDS3 cards, which ran from a long time ago until just a couple months ago when we finally (and literally) pulled the plug on dialup (I think we had about 30 active accounts from a peak of over 35,000). There was a time where NAC was by far the largest customer of the LEC portion of Sprint in NJ, with two DS3's of PRI's out of NWTNJ alone (look that up, it's in the woods in 07860). Sprint had to actually buy software upgrades for the DMS we were out of to accommodate a hunt-group that large (or, so we were told). This was after we had about 700 POTS lines to a house and they begged us to move to the CO. Ahh, the good old days. And it is amazing how well it all worked, in retrospect, and how much fun the business was. Then you see things like "Net Neutrality", and it makes me want to hide in the woods and shed a tear.
We used Livingston Portmaster 3 back in the day. Front to back ventilation, ran cool as a cucumber, plug it in and it just worked. Awesome gear until Lucent bought the company to kill the product in favor of their Ascend TNT space heaters.