Subject: Re: Found DEC branded AU, need specs
To: Gregg C Levine <hansolofalcon@worldnet.att.net>
From: Johnny Billquist <bqt@update.uu.se>
List: port-vax
Date: 01/17/2004 23:59:22
On Sat, 17 Jan 2004, Gregg C Levine wrote:

> Hello from Gregg C Levine
> Here's how it happened. I visit a store in the Canal Street district
> of Manhattan perhaps four times a month. This time I stopped in there,
> and went over their collection of electronics salvage. I'd already
> obtained a batch of AUIs made by Synoptics, and two designed by AMP,
> from the same place so this one was to be expected.
> 
>  It has the Digital trademarked name on it, and the word DESTA on it,
> in capital letters. And then the usual model number, and serial
> numbers, I'll spare them from the list. Does this particular gizmo
> ring any bells for anyone on the list? I might add, that it is an AUI
> configured to be attached to a 10BASE network using coax from the
> traditional AUI attachment (DB15) connector. 

10Base what? 10Base in itself is just another way of saying it's a normal
10 Mbit/s ethernet.

You have 10Base-5, which is the old thickwire, 10Base-2, which is the
thinwire, and 10Base-T, which is the twisted pair. There are a couple
more, which I don't remember right now.

What you have in your hand is a transciever. Old ethernet cards usually
have the AUI connector (the 15-pin thing), and then you used an external
transciever to hook up to the physical ethernet. At the start, there was
only 10Base-5, so you had transcievers which connected to the thick
coax. Normally with a vampire tap. The maximum segment length is 500
meters, which is where the -5 comes from. Since many didn'ät like handling
that thick coax, drilling in it, and spacing transcievers at atleast 2.5
meters distance from each other, 10Base-2 came, in which the maximum
segment length is 200 meters, and unless my memory fails me, the minimum
distance between two transcievers is 0.5 meters.

Okay. So far it's all really easy. So what about more modern cards, on
which you don't have AUI, but instead have the small coax connected
directly, or the TP cable. Well, those have a transciever as well, but
it's integrated on the card. Means you need less hardware, but you cannot
use it for any other physical medium than what the built-in transciever is
for.

By now, it should be obvious that what you have is a 10Base-2 transciever.

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt@update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol