riscy
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Re: Ethernet stuff

To: riscy@pyramid.com
Subject: Re: Ethernet stuff
From: Andreas Busse <andy@resi.waldorf-gmbh.de>
Date: Thu, 8 Jul 93 16:37:05 +0200
Reply-to: riscy@pyramid.com
Sender: riscy-request@pyramid.com
> * DC-DC supply
> 
> We need an isolation between the interface and the tranceiver.
> The NS-databook says that this is an IEEE802.3 requirement.
> (Soory I don't have the IEEE802.3 paper)
> But I think because of potential differences between different nodes.

You may have right that IEEE802.3 requires an isolation between
sender and receiver. Nevertheless, I doubt that this true for
most applications. First, a cheap DC-DC converter doesn't really
isolate. Second, we had some trouble in our office due to a
grounding problem which produced a 100 V potential difference
between two machines. If they were *really* isolated, we would
never had noticed that. Instead, our net silently went down
after a few minutes, and the AUI-BNC adapters where hot enough
to make ham&eggs on them. Fortunally, it didn't break them.

Andy
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