Chapter 4 -
http://bitsavers.org/pdf/dec/terminal/gigi/EK-VK100-TM-001_V...
VK100 (aka GIGI) lets you do ReGIS graphics and optionally download BASIC programs to run on the client. It implements VT52 (ANSI) by default, but you could easily extend it to support full VT102 or VT400 codes too.