You need a PS/2 keyboard for this
The way I have done it, is nether right, nor easy, it works on Intellex DVMS 3, 4 and Ultra. Here it goes:
Restart Intellex unit and press F8 on bootup (we need to start the unit on safe mode, to avoid starting the Intellex program)
In safe mode you need to reset the password, so You need to open "Intellex Configuration"-icon on the desktop. There you can reset the password to default. Be careful, not to reset everything