How do I get an ESC (escape) character on a DEC keyboard?
1. Use F11 on the LK201 or LK401 (in most keyboard modes).
2. Use Ctrl-[ (left bracket)
3. Adjust the keyboard mapping in DECterm, if that's what you're using.
4. Use dxkeycaps to produce commands for xmodmap. See the manual pages
5. Get an LK421-AA keyboard, a North American keyboard designed for UNIX
systems. It has an ESC key, no caps lock, and the keypad has
been removed so the keyboard is smaller.