On Fri, 8 Feb 2002, Pete Turnbull wrote:
The usual concern is not capacity -- if the school
already has copper
it probably is 10baseT or 10base2/10base5 which is the same speed as
10baseFL -- but safety.
Exactly.
You're not supposed to run copper between
buildings for two reasons.
First is that they may not be grounded at the same potential; there
could easily be a voltage difference between them. Even a small
difference can cause damage to interfaces, though if they're working
at present, presumably that's not serious in this case. Tiny
differences just cause increased error rates. However, if there
should ever be an earth fault on one building, all bets are off.
Second reason is inductive pickup, or change in ground potential due
to nearby lightning. Even coax picks that up rather well.
Right. The only reason copper was run between the three buildings was
cost. I did not have a source for transceivers or fiber, and the school
has no budget for the network as it is. The copper has been in a year and
a half or so, and works ok, but I still want to replace it.
The cheapest way to do this is often to find a pair of
hubs (like the
3Com Netbuilders or PSII range) which can take an extra transceiver
module or two in the back. They're usually cheap, and the Fibre Link
interfaces are very cheap because hardly anyone wants them. Standalone
media converters, on the other hand, are much more expensive, even
secondhand.
You wouldn't happen to know someone with 3-4 24 port units they would be
willing to give the school do you? Currently I've got a large number of 12
port 'AMP' brand hubs installed, since thats what I had access to when I
put the cable in. I did install halfway decent patch panels, so patching
in new equipment is very easy.
Best way to buy the fibre for short runs (10-50 yards)
is to buy patch
leads from a trade supplier. Trade suppliers are typically 1/2 - 1/8
the price of end-user catalogues. Better still, sometimes you find
people with surplus patch leads with ST connectors, which they've
replaced with SC or even MT-RJ.
Thats what I had in mind. The condits are dedicated for network cable, so
I can use the existing copper to pull in fiber and or a new pull rope.
-Toth