Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!batcomputer!itsgw!steinmetz!uunet!wa3wbu!john
From: john@wa3wbu.UUCP (John Gayman)
Newsgroups: comp.dcom.modems
Subject: Re: null modem cables
Summary: just one possibility
Message-ID: <626@wa3wbu.UUCP>
Date: 4 Sep 88 14:44:46 GMT
References: <8809030943.AA02215@ucbvax.Berkeley.EDU>
Organization: WA3WBU, Marysville,PA
Lines: 63

In article <8809030943.AA02215@ucbvax.Berkeley.EDU>, A1T@PSUECL.BITNET (Andy Tefft) writes:
> 
>   - - The original note follows - -
> 
> Can anyone out there tell me how to make a null modem cable? I tried just
> connecting corresponding pins of my 2 serial connectors on 2 computers
> together, with the serial cards set the same way. No dice.
> 

    [ My mailer failed to get this through so I'm posting it]


  Andy,

     There are many configurations for null-modem cables. It seems that
each manufacturer wants to see different signals. All the null-modem
cable is doing is crossing over the appropriate signals to make each
computer "think" he's tied to a modem, when in fact their connected
directly together. I have used the following null-modem on dozens of
systems, it uses a couple more wires but it should satisfy anything you
hook it to. On the other hand, the worlds simplest null modem only
uses 3 wires, and works sometimes with terminals. Here's what always
works for me:


	Side A				Side B
        Pin no				Pin no
	------				------

          1  ---------------------------- 1
          
          2  ---------------------------- 3

          3  ---------------------------- 2

          4  --+------------------------- 8
               | 
          5  --+ 

          8  -------------------------+-- 4
				      |
				      +-- 5

          6  ---------------------------- 20

          7  ---------------------------- 7
 
          20 ---------------------------- 6


     I think you see the theory behind this arrangement. Depending on
the equipment, you can get away without certain signals. Im sure you'll
get a lot of different suggestions from your query. Good luck.


					John



---
John Gayman, WA3WBU              |           UUCP: uunet!wa3wbu!john
1869 Valley Rd.                  |           ARPA: john@wa3wbu.uu.net 
Marysville, PA 17053             |           Packet: WA3WBU @ AK3P