Mystery box

der Mouse mouse at Rodents.Montreal.QC.CA
Thu Jul 21 12:31:38 CDT 2005


>> I've used a DC37 (note, AFAIK the DB37 does not exist,
> http://www.pccables.com/00830.htm
> http://www.mycableshop.com/3rd_Level/Switchbox-DB37.htm

The former is, and the latter almost certainly is, a DC37 mislabeled as
a DB37.

There is a tendency - which I must admit I participated in for some
time, until I learned better - to call any D-shell connector a DB.
This is wrong.  The DB size is the one usually used for 25-pin.

The sizes and their canonical pin counts are

DA	15-pin, such as used for AUI Ethernet or peecee joystick/MIDI
DB	25-pin, such as used for RS-232C serial ports and peecee
	  parallel ports
DC	37-pin, such as in http://www.pccable.com/images/00830.jpg or
	  the box which started this thread
DD	50-pin, such as used by old Sun-3s for SCSI
DE	9-pin, such as used by peecee serial ports, and sometimes video

This is why you may find the 15-pin VGA connector called a DE15,
because it is (it's a DE shell with 15 pins) - and the "DB37" that
pccables.com is selling is actually a mislabeled DC37.  (I feel sure
the one from mycableshop.com is too, but I didn't see any obvious
pictures there.)

Like Tony, I've never seen a real DB37 and am inclined to doubt such a
beast exists.  Other sizes do exist, but they are rather nonstandard;
for example, (some?) NeXT grayscale machines' monitor connector was a
D-shell connector with, if I recall, 19 pins - somewhere between DA and
DB size.  (You could make a mechanically compatible connector by
removing pins from a DB25M or by cutting away part of one end of a
DB25F, though I don't know of anyone who's actually done either.)  I
suppose you could call it a DA.KKKKKKK... connector, but that would be
excessively geeky :) and doesn't account for the way DE is actually
*smaller* than DD.  (I assume DE was an afterthought.)

>> although the DB44 does)

!!  Interesting.  Where'd you see that, Tony?

> Moreover, the DB25 connector is technically not a part of the RS-232
> spec.

It was back when I got a copy of RS-232C by interlibrary loan, some ten
or fifteen years ago.  Unless you're drawing a distinction between
RS-232 and RS-232C which is lost on me.

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