Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!apple!sun-barr!decwrl!shlump.nac.dec.com!shodha.dec.com!elvira.cxo3.dec.com!ridder
From: ridder@elvira.cxo3.dec.com (Hans Ridder)
Newsgroups: comp.sys.amiga.tech
Subject: Re: RS232 gender (was Re: Apple SCSI not compatible with standard SCSI?)
Message-ID: <511@shodha.dec.com>
Date: 4 Dec 89 22:34:15 GMT
References: <856@lpami.wimsey.bc.ca>
Sender: news@shodha.dec.com
Organization: Digital Equipment Corporation, Customer Support Center
Lines: 82

To: lphillips@lpami.wimsey.bc.ca
Subject: Re: RS232 gender (was Re: Apple SCSI not compatible with standard SCSI?)
Newsgroups: comp.sys.amiga.tech
In-Reply-To: <856@lpami.wimsey.bc.ca>
Organization: Digital Equipment Corporation, Customer Support Center
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In article <856@lpami.wimsey.bc.ca>, lphillips@lpami.wimsey.bc.ca writes:
>In <503@shodha.dec.com>, ridder@elvira.cxo3.dec.com (Hans Ridder) writes:
>>RS-232 (now EIA-232) has, for quite a while specified the gender of
>>connectors....
[my interpretation of EIA-232 deleted]
>
>The last time I read the spec, which was when I made a statement about the
>gender issue, and was corrected, it did not state the gender for the DTE. I
>would be interested in knowing if your copyof the spec actually says that or
>if you are just choosing to interpret it that way.

Well, to a certain extent I was reading what I wanted to see.  I've
been reading alot of RS-449 and EIA-530 lately and they specify the
DCE *and* DTE connector clearly.  Anyway, the *exact* text in my copy
(probably the same as yours) says:

  (The following is copyright 1981 Electronic Industries Association,
  included without permission.  Though I don't think they mind)

  "3.1 The interface between the data terminal equipment and data
  communication equipment is located at a pluggable connector signal
  interface point between the two equipments.  The female connector
  shall be associated with, but not necessarily physically attached to
  the data communications equipment and should be mounted in a fixed
  position near the data terminal equipment.  The use of an extension
  cable on the data communication equipment is permitted.  An
  extension cable with male connector shall be provided with the data
  terminal equipment.  The use of short cables (each less than
  approximately 50 feet or 15 meters) is recommended; however, longer
  cables are permissible, provided that the resulting load capacitance
  (C(L) of Fig. 2.1), measured at the interface point and including
  the signal terminator, does not exceed 2500 picofarads.  (See
  section 2.4 and 6.5.)

    3.1.1 When additional functions are provided in a separate unit
    inserted between the data terminal equipment and the data
    communication equipment (See section 1.7), the female connector,
    as indicated above shall be associated with the side of this unit
    which interfaces with with the data terminal equipment while the
    extension cable with the male connector shall be provided on the
    side which interfaces with the data communications equipment."

What I find bizzare here is this concept of an "extension" cable on
the DTE.  Heck, even the DCE connector "mounted in a fixed position
near the DTE" is a pretty strange concept.  I *believe* they were
thinking that all DTE's would have a cable coming out of them with a
male connector on the free end.  Sort of like the old DEC LA36's and
VT52's had.  And that *some* DCE's might have such a cable too.

You're right, they never get right down and say "the male connector
shall be associated with the DTE".  But they do say that the DTE will
be provided with a cable with a male connector.  I would say that the
connector mounted directly on the DTE is just the special case of a
zero length "extension" cable.  That, and the stuff in section 3.1.1
about connectors on "inserted" units sure makes me think they intended
male connectors to be on DTE's or DTE-like equipment.

Anyway, I can certainly see that the words are ambiguous, or at least
open to some interpretation.  Aren't standards wonderful?  You'd think
they would clarify things like this, but nooooooooo.  By the way, is
the text in your copy of the spec any different?

>I am not interested in gender wars. I am interested in facts.
>
>-larry

Neither am I.  Scouts honor, I was trying to head off a war.  I hope I
didn't start one though.... :-)

-hans
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  Hans-Gabriel Ridder			Digital Equipment Corporation
  ridder@elvira.enet.dec.com		Customer Support Center
  ...decwrl!elvira.enet!ridder		Colorado Springs, CO