The Electrical Switch will be slightly lower and to the left of the Terminal. You can now get the MIRV without having to find the Keller Family Transcripts. Or, you can use aglitch, where you Just go into Third-Person View, and move your analog stick and look for a different activation line saying 'Activate Electrical Switch'. To acquire this weapon, you must first complete the Keller Family Refuge, because after completing this, you will have access to a secure section of the National Guard Depot, where the MIRV will be sitting next to the skeletons of the Keller Family.
This is a special upgraded version of the Fat Man.
The most powerful weapon on Fallout 3 is not the alien blaster or the gauss rifle, but the Exerimental MIRV.
