Re: strange network problem
On Thu, Nov 02, 2006 at 01:00:50PM +0100, Erik Mouw wrote:
> Europe has unearthed plugs only for double insulated equipment (which
> can be recognised by a symbol resembling two squares in each other).
> Double insulated equipment comes with the flat unearthed "europlug"
> that is supposed to fit in all sockets, earthed or not (except of
> course in the UK which uses a different socket).
>
> Note that the europlug is a lot safer than US plugs: with the europlug
> it is impossible to touch the life wire through the metal because the
> poles are made from plastic with only a small metal tip. The tip is
> already well in the socket before it actually connects to the life
> wire, the still visible plastic part of the pole can be touched without
> hazard. In the US the poles are made from metal so it's quite easy to
> hurt yourself (but hey, 110V is a lot "safer").
The north american plugs also bend much easier and are often bent when
you pull them out unless you are very nice to them.
> Most if not all desktop computers aren't officially double insulated so
> they need to be earthed and come with an earthed plug. Unfortunately
> lots of older houses still have unearthed sockets and the earthed plugs
> fit quite easily. Current regulations require earthed sockets in all
> new houses (or rather: for all new electrical installations). If you
> really don't have a grounded socket for your computers, make at least
> sure that the ground wires from all computer equipment is connected to
> each other (easy to do with an earthed extension socket). Better is of
> course to have the socket replaced by an earthed one.
I think all houses I have seen built in the last 35 years have all
earthed outlets. Older than that very well might not have earthed
outlets. Old buildings have a tendancy not to be kept in north america.
We apparently always want new. Historic value has little meaning here.
> Yeah, I agree the UK system is silly and has ugly bulky plugs. I guess
> the idea is to protect the cable from the plug to whatever is connected
> to the other end of the cable. That would only make sense if you don't
> have fuses in the electrical panel.
I wonder if it is a leftover from when people didn't have fuses in the
electrical panel, or proper lightning rods or anything else. I know my
dad has told me when he was a child in the 50s lightning storms could
cause interesting sparks and such coming out of outlets, which of course
you don't see anymore.
> Europe doesn't need such plugs because over here earth and ground are
> two different and unconnected things, whereas in the US and Canada they
> are usually connected together at the electrical panel (at least it was
> like that in the houses I've seen in New York state). The ground wire
> is the ground for the electrical system. It can and is allowed to have
> a different potential from the earth (within limits, of course). The
> earth wire is connected to the earth by a metal wire burried a couple
> of meters deep into the earth.
Certainly true as far as I can tell. It does seem that ground and
neatral are considered one and the same for many things here.
> There are still some places in Europe where you actually have two life
> wires operating at 115V wrt to the ground instead of a 230V life wire
> and a ground. The reason for this is that if you balance a 3 phase
> triangle system properly you don't need the ground wire and hence you
> can save 25% on copper wiring. Right now this is seen as dangerous
> cause equipment with a single switch can still be life, so houses are
> converted to connect to a 3 phase star configuration with ground wire.
> (It was however nice cause without a residual current detector you
> could run US 110V equipment without a transformer by connecting it to
> one of the life wires and earth.)
I thought it was usually that you had 230V between neatral and a live
wire, and about 400V between a pair of live wires (out of the 3
available). That is what I remember being the standard setup in denmark
at least. Here we have 2 phase to residential with 230V between them
and 115V between one and neatral/ground. What countries ran the other
way?
> That's possible in Europe because earth and ground are not the same
> thing.
It ought to be possible here since earth and neatral should only become
the same thing at the electrical panel.
> Another great card is the Western Digital/SMC WD8013 (or even the 8
> bit ISA WD8003). It uses the same 8390 chipset as the NE2k, but its
> packet buffer is memory mapped where the NE1k and NE2k have their
> packet buffers only reachable through slower IO space. Back in the old
> days I could easily flood a thin ethernet using a 8003 in a 386DX40 :)
I never used the WD cards. I remember SMC made some awful chips that I
didn't get along with.
--
Len Sorensen
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