Out wonderful telcom system was designed by the department of redundacy
department.
Ben Scott wrote:
On 8/10/06, hewitt_tech <[EMAIL PROTECTED]> wrote:
This discussion reminds me of a Murphy's Law corollary - "An expensive
transistor being protected by a fast acting fuse will protect the
fuse by
blowing first!".
Heh. I've heard a variation on that before -- appropriately enough:
"A $1000 UPS will sacrifice itself to protect a 5 cent fuse".
Seriously though, in the military communications sites
derive all their power from an inverter being fed by two series of
Excide
battery strings.
Yah, the commercial telephone companies do the same thing. In a
telco CO (central office), *everything* runs off of 48 VDC -- even the
lights in many installations. They run off batteries which are
continuously trickle charged. If line power fails, the batteries just
stop charging for a while. They use two sets of batteries, two
charging sets, and two power distribution wiring. All the equipment
has two power inputs. Most COs have an auto-start generator, too.
It's really the right way to do things.
I often wonder why the IT industry doesn't come up with something
along those lines. While redundant-everything is more then most
people want, the flow of power is much more appropriate. With a
conventional setup, we convert from AC to DC to AC to DC, as we go
from line to UPS to computer power supply to computer. It would be
nice if we could leave the inverter out, leave the PC PSU out, and
just go from AC to DC in the UPS, and then run DC directly into the
PC. Less heat, less space, more efficiency, longer runtimes. I'm
sure if, say, APC teamed up with Dell, they could make quite a
killing.
-- Ben
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