Path: utzoo!attcan!uunet!yale!bunker!stpstn!aad
From: aad@stpstn.UUCP (Anthony A. Datri)
Newsgroups: comp.dcom.modems
Subject: Re: null modem cables
Message-ID: <2066@stpstn.UUCP>
Date: 7 Sep 88 17:43:40 GMT
References: <8809030943.AA02215@ucbvax.Berkeley.EDU>
Reply-To: aad@stpstn.UUCP (Anthony A. Datri)
Organization: The Stepstone Corporation, Sandy Hook, CT
Lines: 35


I was wary of trying to respond to that path via mail, so here goes:

For many things, a null-modem cable merely means a cable wired thus:


2----3
3----2
7----7
20--20

A full-blown, general-purpose null-modem cable would be thus:

1---------1  (always friendly to include the frame ground)
2---------3
3---------2
4---------5
5---------4
6--------20
7---------7
8---------8  (often varies, often not needed)
20--------6

In short, pins 1,7,8 wired straight, 2x3, 4x5, 6x20.
The 4-wire form works for most things (terminals, printers),
the full-blown is for things that want hardware handshaking.
And, of course, if you've got something like an MTI mux or
(shudder) a DMF-32, everything's screwy.


-- 
@disclaimer(Any concepts or opinions above are entirely mine, not those of my
	    employer, my GIGI, or my 11/34)
beak is								  beak is not
Anthony A. Datri,SysAdmin,StepstoneCorporation,stpstn!aad