didn't someone tell me that telco equipment had 40vdc racks once?

[Armantrout, Fred]

This summer while checking out possible new data centers, one our eval
outings our team visited was a former telephone crosslink site.  It was
over in Shawnee.  That site HAD 48V DC and a significant DC bus system
installed.  There was lots of shiny copper and an impressive power / UPS
room.  

On what could connect to it.  Looking at the options, I think some of
the HP ProLiant systems have Telco versions that can be fed DC rather
than standard AC power supplies.  One in particular, the HP P-class
Blade servers has external power sources and they feed 48V DC into the
chassis.  HP even has a rack power setup that can stack multiple blade
chassis and tie it all to a 48V system or a common AC/DC supply to stack
them.

You DON'T want to drop a screwdriver across it or you WILL see stars.

Fred Armantrout
Burns & McDonnell Engineering Co.