I figure a $120 APC or Tripp-Lite battery backup UPS (Uninterruptible Power Supply) could keep a 551x working through a power cut, though not sure how well the UPS would like the large surge from initial power up/down of the large linear power supply transformer in the 551. I use a UPS to protect my business phone system and A/V equipment from random power cuts.

For some reason the local power substation likes to explode from time to time, once it sent a surge so large it blew up 3 devices; my business phone system's power supply (an AT&T 1080), a DVD player, and something else I can't remember. I opened the DVD player and found the power protection varistor had blown completely, and left a large black spot on the board and on the metal chassis. Replaced the varistor to fix the player, and had to replace the phone system wall wart.

BTW, I did locate my old backgammon case which I'd used for various industrial purposes over the years. The board fits inside perfectly.. here's an actual pic (instead of the obvious photoshop mockup I'd posted earlier in this thread):

[Linked Image from seriss.com]

I guess I could mount it to a board that fits inside, so I don't have to drill through the case.