
The third-party media adapters are usually cheaper (at least in Toronto) than
Apple's. I bought the adapters from Asante instead of Apple.


That's not true. Only the DECstation 5000/200 comes with a Thinwire
(BNC, coaxial) Ethernet connector. The 5000/25, 5000/133 and 5000/240
all have a single 15-pin AUI Ethernet connector only. I distinctly
remembered this because when got the 5000/200 first and I thought all
of them are going to be Thinwire. I eventually had to go back and ordered
DESTAs (DEC's oversized version of an AUI-to-BNC adapter that MUST be used
with a transciever cable) for the rest of the stations.

My advise to the very original poster (Beverly?) is:

(1) If all you want is to create a LAN with two workstations and won't add
    machines to it EVER, go for Thinwire regardless of the media type. Going
    for UTP (unshielded twisted pair) wiring requires a concentrator which
    means extra money and I believe these units come with at least 6 ports.
    As for Thicknet, it's a nightmare and cabling is expensive. Avoid it
    unless you have no choice (e.g. the two machines are two floors parts).

(2) On the Mac side, you will need:
    - one Thinwire media adapter (from Apple or third-party).
    - MacX (make sure you get version 1.2; 1.1.7 won't run on System 7.1).
    - MacTCP (which comes with MacX; if you get MacX v1.2, you should be
      getting MacTCP v1.1.1 with it. Don't use earlier versions on a Centris).
    - you may or may not need a 25ohm terminator depending on the
      Thinwire media adapter. So just ask the sales if the adapter is
      self-terminated or not.
    - configure MacTCP to use "Ethernet".

(3) On the DECstation side, you will need:
    - for a Model 200, you will only need a T-connector.
    - for Models 25, 125, 133, 240, you will need an AUI-to-BNC adapter.
      Get one that can be plugged in directly to the AUI port of the
      DECstation. This way you save the cost of a transciever cable
      (a 15-pin AUI male to a 15-pin AUI female cable).
    - get a 25ohm terminator.

Your two-machine network will look like this:


       ##T----------------------------------------------[]
      +-----+                                           |
      |     |                                           |
      +-----+                                         +-----+
                                                      |     |
                                                      +-----+
    DECstation                                        Centris
     5000/200                                           650
                              OR

       ##T----------------------------------------------[]
        {=}                                             |
      +-----+                                           |
      |     |                                         +-----+
      +-----+                                         |     |
                                                      +-----+
    DECstation                                        Centris
5000/25,125,133,240                                     650
         
   ##    -> 25ohm terminator
   T     -> T connector
   ---   -> Thinwire (RG58 coaxial cable)
   {=}   -> AUI-to-BNC (i.e. Thick-to-Thin) adapter
   []    -> Thickwire media adapter (assuming self-terminated)
   |
   |

Andy