Path: utzoo!attcan!uunet!ncrlnk!ncr-sd!hp-sdd!sceard!mrm
From: mrm@sceard.UUCP (M.R.Murphy)
Newsgroups: comp.sys.att
Subject: Re: standards and ATT
Summary: all of 'em are different
Keywords: RS-232
Message-ID: <859@sceard.UUCP>
Date: 17 Nov 88 20:34:48 GMT
References: <851@sceard.UUCP> <1415@neoucom.UUCP>
Reply-To: mrm@sceard.UUCP (0040-M.R.Murphy)
Distribution: na
Organization: Sceard Systems, Inc., San Marcos, CA  92069
Lines: 75

In article <1415@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
>
>You still left us hanging; does the DTE have a DB25S or a DB25P on
>it?  The lastest issue I have is the August 1969 EIA RS-232-C
See below.
>specification, and it only recommends that the connectors have 25
>leads; it doesn't specify physical form factor.
>
>It seems to me that previously most DTEs had sockets and therefore
>required an extension cord with plugs on each end and leads 1,2,3,
>4,5,6,7,8 and 20 wired straight through.  That made VT-100s and IBM
>XT serial ports the odd men out.
Not quite, see below.
>
>Using DB25S connectors on the 6386 WGS is consistent with other DTE
>devices that AT&T sells.  I have an Intelliport 8 port board in my
>IBM model 80, and that fans out to DB25S connectors too.
Not quite, see below.
>
>Unfortunately, I believe we shan't ever see a standard-conforming
>RS-232 connector.  I like the MIDI serial connectors used to
>wire synthesizers together:  reasonable baud rate (31250), only one
>type of cable, and only one way to hook things up.  Totally idiot
>proof (well, almost!).
>
>--Bill

I think that that was me that left us hanging. Sorry.
The 6386WGS is a nice box. It is a DTE. With the 802 it has 9 serial
ports. One is on the back of the CPU box. The RS-232 serial port on the back
of the CPU box has a DB25p. The 8 serial ports on the 802 have DB25s's.
The 2 parallel ports on the 802 have DB25s's. This is to make it easy to
plug a serial device into a parallel port. Or maybe to make it easy to
plug a parallel device into a serial port, who knows? I calculate that the
correctness factor for a serial DB25p on a DTE is therefore 0.111... :-).

This may be because some folks view a terminal (as in VT100 terminal) as
a DTE and think that the computer to which the terminal is attached is
a DCE. Not so, they are both DTE's. It's the thing that connects 'em
to each other that is a DCE. That may be as simple a device as a null
modem, a cable wired as a null modem (horror of horrors), a pair of
modems with a pair of wires between 'em, or the entire humongous DDD
network (probably a trademark of somebody) between. DTE's outta have DB25p's
and DCE's oughtta have DB25s's.

If anyone is really interested, the standard is EIA-232-D.
(ANSI/EIA-232-D-1986, approved November 12, 1986).
This standard is a revision to RS-232-C, which brings it in line with
CCITT V.24, V.28 ans ISO IS2110.

Paragraph 3.2.1 states Figure 3.1 illustrates the DTE connector which has
male (pin) contacts and a female shell (plug connector). Figure 3.2
illustrates the DCE connector which has female (socket) contacts and a male
shell (recptacle connector).  One might also check out EIA-530-D.
Up until this was a standard, this was just the way that folks who knew what
they were doing did it. Now it's a standard. Nice if the folks who are now
doing it would follow the standard (which can be ordered from

    ELECTRONIC INDUSTRIES ASSOCIATION
    Engineering Department
    2001 Eye Street, N.W.
    Washington, D.C.  20006

and which was $20.00 (US) at time of publication. Who knows now?)

Thanks are due to A. Philip Arneth, who for over 24 years worked on this
standard.

I give up. I'll just go to Radio Shack (registered trademark of TANDY:-)
and buy a whole bunch of 9-pin, 15-pin, and 25-pin connectors and wire
and build adapters as I need them. That's what we've all done in the past,
and there certainly is no reason to change now.
--
Mike Murphy  Sceard Systems, Inc.  544 South Pacific St. San Marcos, CA  92069
mrm@sceard.UUCP       {hp-sdd,nosc,ucsd}!sceard!mrm            +1 619 471 0655