24 Mar
2001
24 Mar
'01
8:32 a.m.
On Mar 24, 9:44, Bill Gunshannon wrote:
As far as I've seen, it's always been available in 100m and 500m drums --
which of course happen to be multiples of 2.5m -- but I'm sure that's just
because they're nice round numbers. Most cable is sold in those
quantities.
One of my catalogues does list 10,20,30, and 40m lengths fitted with
N-connectors, but again I'm sure that's just because they're round numbers.
Agreed, but that was *common* practice.
I have a pair of FOIRL transceivers and some fibre for exactly that, but
people still are interested to see real Ethernet.
On Sat, 24 Mar 2001, Pete Turnbull wrote:
> I've not seen anything about lengths, except
of course for the maximum
> length and multiple-of-2.5m tap separation. I'm told the standard
> specifically allows for lengths to be joined at intervals which are
*not*
multiples of
2.5m, and the overall length does not have to be an exact
multiple either.
Well, I could be wrong, but back in the days when I actually did this
stuff for real I know I never saw yellow cable sold in bulk. Only in
fixed lengths. One would hardly expect they did this if there was no
reason for it. I doubt I still have any catalogs from those days to
look at. In any case, I doubt anyone is going to do a real network today
with an really long sections of yellow cable.
> I've never been aware of a problem with that.
Our old Departmental
network
> (installed by my predecessors) consisted of
several segments, many of
which
> had lots of N-series transceivers in them. I
suppose, though, that
when
> using N-series transceivers, it might make some
sense to chop out a
small
piece of coax
rather than just cutting it.
Boy, that sounds scary. But then, what you see in practice does not
always reflect good practice. In the early days of ethernet, all kinds
of strange (and even dangerous) things were done. Like grounding both
ends of the yellow cable (no, you are not supposed to do that!!)
Yup, I know! I saw what hapenned when someone tried that :-) It did *not*
do anything any good at all! I also know what can happen when the unwary
(in this case, me) touch the screen while holding on to a locally-earthed
cabinet :-)
Or thin-net installations with a length of RG58
between the T-connector
and the transciever.
I know someone who tried that, too. It worked for a couple of short tees,
but after that everything fell apart. I know of a few installations which
use Safernet and EAD cable to prevent people trying it.
Unless
they're a long way apart, or you're doing it for
demonstration/nostalgic/"because it's there" purposes :-)
I can see doing for demonstration purposes, but I would bet people would
be more impressed if it was fiber. That's what I use small demos. And I may be able to find stuff (like vampire taps) at
work as
although it is all inactive, I doubt that the yellow cable has been
removed from the ceiling and wiring closets. Who knows, maybe they
would even be glad to have the yellow cable pulled out too. It's a
pretty long run (the length and height of the building) in two sections.
I'd like to get a vampire tap for my collection -- all of ours were
N-series, at least all the ones I've found.
--
Pete Peter Turnbull
Network Manager
Dept. of Computer Science
University of York