3174 Terminal Controller

Well, this has been one of those ideas that has been at the back of my mind for a long time - I would like to interface one of these IBM terminals I have around the house to something. Anything. I was thinking about an emulated mainframe on Hercules or something. But the thing that brings this to the foreground in my thoughts is that today I had to troubleshoot a 3174-51R at a customer's site. This thing is connected, via a rather unusual cable, to a Cisco 2500 series router, so that means the 25 pin connector on the back must be some form of X.25 or something like that. I know that the fellow at corestore.org has been able to get a real IBM terminal to telnet into an emulated system via a terminal controller with built in ethernet (although I have never seen one). Anyone done this before? What do I need to hunt for? I now have one piece of the puzzle that I was never able to find before - the manual for the 3174-51R. Now the terminal controller's operation can be deciphered. But, of course, I don't have the 3174. -Ian