I remember the Integrex, came out in the later 70's if I remember correctly, I wanted one for my Viking Compact 88.
I just happened to be dumpster diving one day and snatched a Teac AN180, then a couple weeks later found another Teac AN 180.
I was lucky enough to get replacement op amp chips (noisey) and after that it works like a champ.
It will encode and decode, sounded pretty good playing back pre recorded tapes on my Revox A77.
If anyone is looking for an outboard Dolby unit I would suggest the Teac.
bob