I have a copy of some TTY documentation (describing the TTY driver code, what it is, what it does etc.) Written by Jan Charvat () and Barnett Hsu (). It's in TeX, with a Fig Figure. I haven't had time to read it over in detail, but it might be worth asking for, at least as a basis of more info for the KHG. There's no copyright on the document so I won't put it up for people to read, but someone might like to get in contact with the authors and I presume that I can pass it on to people.