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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.dcom
Subject: Re: Office networking ala RS-232
Message-ID: <6674@utzoo.UUCP>
Date: Sat, 10-May-86 23:28:51 EDT
Article-I.D.: utzoo.6674
Posted: Sat May 10 23:28:51 1986
Date-Received: Sat, 10-May-86 23:28:51 EDT
References: <532@gould9.UUCP>, <11620@amdcad.UUCP>
Organization: U of Toronto Zoology
Lines: 21
Keywords: patch panel, cabling

> >First, how many wires would I need?  I was guessing 6 but a lot of
> >the stuff I've seen suggests 8 (TD,RD RTS, CTS, DSR, SG, DCD,
> >DTR) or 9 (add FG)...
> 
> You can get by with 6 for terminals and modems (TD,RD,DTR,DCD,SG)...

Actually, for terminals (and only for terminals) you can get by with 3
wires (TD, RD, SG).  We do this routinely.  This does mean that (a) you
have no hardware indication of the user switching off his terminal (add
DTR if you need this) and (b) if the terminal needs flow control, it and
your software better be capable of using XON/XOFF (add CTS and RTS if
you need hardware flow control).  You will need DCD and RI, and perhaps
DSR, for modems.  We actually tend to use full 25-wire cable for modems,
although that is considerable overkill.  Note that you will quite possibly
have to do some jumpering on one or both ends with the minimal schemes;
your machine probably wants to see DCD on terminal lines (jumper it to DTR)
and some terminals want to see various signals before they will talk (we
jumper CTS, RTS, DSR, and DCD together as a generic solution).
-- 
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