The 520ST that I have has tos in rom. I plugged in the terminal cart and hooked up the nill modem cable and they were off! I had them hooked eogether and they were working. The 520 I have is an early one, and based on my reading the early st's had tos in rom, like this one that I have. I can't transfer anything cause there's something wrong with the controller on the atari (among other things). But yeah, I just got iff the st and I was talking with terminal just now. I think there was a miscommunication. The st has the tos in rom and boots without a fdd. It can't do much, but it'll boot and give me the green desktop. I definitely am in the process of biting the bullet (delorme searching) but I think I wasn't being verry descriptive.
The term cart works with the st's rom and makes it a terminal and can go back to desktop mode with the cart on the desktop as little "c". This thing is neat! It has the manual and everything. I wonder if it'll talk to a unix machine...?
And about this ST. The keyboard needs to be replaced SO bad. It's lived a long, hard life and it needs love. The keys on all the left side are very sticky and you have to hit them like stubborn buttons. The top half of the case has small caracks in it, there are three keys missing off of it, one of the screw sockets(?) is broken by the power led so it comes up. All the connectors are a little bit rusty in the back and it has a bunch of scratches on it. Not a good fetch if I were to buy it. This was given to me.