Newsgroups: comp.dcom.lans.ethernet
Subject: Re: Has anyone ever seen a crossover AUI cable?
References:  <[email protected]>
glen herrmannsfeldt  writes:

> The Eighth Doctor wrote:
> 
> (snip)
> 
> > Anyway while searching for solutions, and found them, I came across
> > an e-mail embedded in a webpage regarding a crossover AUI cable
> > described inside Tomi Enghdahl's terrific website.
> 
> AUI is not symmetrical, and passive crossovers can't work.

You are right that AUI is not symmetrical. 

But according this Usenet news article that is archived at 
http://www.epanorama.net/documents/lan/aui2aui.html 
a suitable passive crossover could work on some cases:


Newsgroups: comp.dcom.lans.ethernet
From: [email protected] (Matthew Deter)
Subject: Re: AUI to AUI cheaply, how?
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
X-Newsreader: TIN [version 1.2 PL1]
Date: Sun, 13 Mar 1994 17:45:17 GMT

Jay Hennigan ([email protected]) wrote:

: I, too have a similar need, and turned to this newsgroup for the express
: purpose of asking about pin numbers!  Tell us about your experience of 10
: years ago.  I've got plenty of experience in making cables and the right
: tools, but just need the pin numbers if in fact it is doable.

The following is a reply I received when I asked this exact same
AUI <-> AUI "null modem" question a while back.  (I forget which group
I asked on...)

I **DID NOT** try out this wiring diagram, as the need evaporated
before I had a chance to try it out.  (I found some BNC transceivers
laying around.  :-)

**Try this at your own risk.**

---BEGIN INCLUDE---

From [email protected] Wed Oct  6 02:43:18 1993
Date: Wed, 6 Oct 93 10:42:20 BST
From: "Andrew J V Yeomans" 
Subject: AUI <-> AUI cabling question

I've done the following, and got it to work. No promises, try at your
own risk!

                Shield   1              1  Shield
    Collision Detect A   2              2  Collision Detect A
       Transmit Data A   3 ----\ /----  3  Transmit Data A
  (Receive Data Shield)  4      X       4 (Receive Data Shield)
        Receive Data A   5 ----/ \----  5  Receive Data A
                    Vc   6 ---     ---  6  Vc
        (Control Out A)  7    |   |     7 (Control Out A)
   (Control Out Shield)  8    |   |     8 (Control Out Shield)
    Collision Detect B   9 ---     ---  9  Collision Detect B
       Transmit Data B  10 ----\ /---- 10  Transmit Data B
 (Transmit Data Shield) 11      X      11 (Transmit Data Shield)
        Receive Data B  12 ----/ \---- 12  Receive Data B
                    V+  13             13  V+
             (V Shield) 14             14 (V Shield)
        (Control Out B) 15             15 (Control Out B)
--
Andrew Yeomans  081-818 4288         NOSS/VNET: BASVM1(YEOMANA)
Internet: [email protected]      IEA:   GBIBML89 at IBMMAIL
IBM  Ltd, 1 New Square, Bedfont Lakes, Feltham, Middx, TW14 8HB

---END INCLUDE---
--
   $$    Matthew Deter
  $$$$   [email protected]
 $$
  $$$$   "The fortune of my spirit is not to be blown into coins of brass
     $$   and flung to the winds as alms for the poor of the spirit."
  $$$$
   $$                              -- from the novel _Anthem_ by Ayn Rand


> There are active devices, the most famous one is called DELNI,
> which can be used to perform the function that you ask.
> 
> I also used to have two and four port transceivers that,
> when properly terminated, would perform that function.
> 
> My first work with thick ethernet used two and four port
> transceivers.  One day I was having problems with a two port
> that had been working.  After working on it for a while, I figured
> out that it failed when a transceiver cable was connected to the
> unused port without a host.  I then built my own AUI terminators,
> and complained to the company that made them.  There answer was to
> send us some AUI terminators.  The four port version didn't have
> that problem, though.
> 
> -- glen
> 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/