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From: ian@sibyl.eleceng.ua.OZ (Ian Dall)
Newsgroups: comp.sys.nsc.32k
Subject: Re: Gatewayed mail message
Message-ID: <901@sibyl.eleceng.ua.OZ>
Date: 6 Apr 91 00:53:59 GMT
References: <9104041201.AA01629@guug.guug.de>
Reply-To: ian@sibyl.OZ (Ian Dall)
Organization: Engineering, Uni of Adelaide, Australia
Lines: 39

In article <9104041201.AA01629@guug.guug.de> stacey@guug.de writes:
>To:	pc532@daver.bungi.com
>Subject: PC532 RS232/V24 Serial Ports are DTE, (DCE is normal for a host).
>From:	stacey@guug.de (Julian Stacey)
>
>The PC532 breaches normal convention, it should have been configured DCE !
>Why was the PC532 IDC configured as DTE ?

>Abbrevs. used:
> DTE = Data Terminating Equipment (VDU/VDT/Terminal/Printer)
> DCE = Data Communicating Equipment (modems, & multiple port host computers)

Actually, DTE is correct. Computers, regardless of the number of ports are
DTE. This is because RS 232 assumes you will always communicate with some
modem. Thus the "classic" RS 232 situation is

  VDU======Modem--------Modem=====CPU
 (DTE)     (DCE)        (DCE)     (DTE)

This is why the term "null modem" is used for a crossover which lets two
DTE ports talk to each other.

Now to confuse the issue, some computer manufacturers said "most ports are not
connected to a modem, so lets make it easier for people by wiring our ports
DCE". This is *not* correct. Also some VDU manufacturers said "most VDUs are
not used via a modem, so lets make it easier for people by wiring our ports
DCE". This also is *not* correct.

Of course, for devices which don't fit into any of the classifications
VDU, Modem, or CPU, the correct choice is uncertain.  This, when
combined with the variety of flow control implimentations and
connector sexual compatability issues makes RS 232 a crock of shit.
However, it is not going to go away now and it is correct for the
PC 532 ports to be DTE.
-- 
Ian Dall          I'm not into isms, but hedonism is the most
                  harmless I can think of. -- Phillip Adams
  ACSnet: ian@sibyl.eleceng.ua.oz
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