[rescue] D-shell nomenclature (was Netra T1 AC200 Questions)

Robert Darlington rdarlington at gmail.com
Sun Feb 14 22:11:16 CST 2010

Wow, thanks for this info.  I had no idea about this stuff and have been
calling them all "DB" connectors without ever giving it any thought.


On Sun, Feb 14, 2010 at 8:45 PM, der Mouse <mouse at rodents-montreal.org>wrote:

> > how to build an RJ45 to DB9 (I'm assuming it's DB9, although I've
> > also heard DE9 for a standard PC serial connector)
> It's properly DE.
> The letter indicates the size of the shell; a DB connector has the same
> size as the 25-pin connector that is standard for serial ports (yes,
> RS-232 specifies the connector as part of the standard) and also used
> for various other things, such as peecee parallel ports and older
> Macintosh SCSI.  DB is usually used with 25 pins (or at least pin
> positions), but sometimes other things, such as the way Sun and SGI and
> probably others put three co-ax connectors and 10 pins in a DB shell
> for video (and usually call it 13W3).
> However, a lot of people make the same mistake I did for years and use
> DB for all of them; I've even seen vendor catalogs exhibit this
> misunderstanding.  However, this loses information; for example, under
> that nomenclature, a "DB-15" could mean either the one properly called
> DA-15 (used for peecee joystick/MIDI ports and, with a slide latch, for
> AUI Ethernet) or the one properly called DE-15 (the higher-density one
> used commonly for video on peecees and very little else).
> The order of the letters is a little odd.  DA is the 15-pin one, DB the
> 25-pin one, DC is almost never used and I'm not even sure how many pins
> it has room for at the usual spacing (37 or 39, I think), and DD is a
> large one that usually holds 50 pins in three rows, used by old Suns
> for SCSI and IPI, and probably other things by various people.  DE is
> the small one, most often with 9 pins as used by peecee serial ports,
> but also used with 15 pins in a higher-density three-row arrangement
> for video.  I conjecture that someone specced out A, B, C, D in
> increasing size, then realized too late that something smaller than A
> was needed, couldn't retcon the existing names, and wasn't geeky (or
> perhaps daring) enough to call the new one D at .
> Other sizes of D-shell connectors exist, but are relatively rare.  The
> only example I can think of offhand is a 19-pin variant that fits in
> between DA and DB in the DE-DA-DB-DC series, used by NeXT for carrying
> video and power from CPU to the human interface and carrying keyboard
> and mouse input the other way (and possibly other things - eg, I think
> sound may have been included on it; it's been a while).
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