From: firstname.lastname@example.org (Bob Wilson)
Subject: Re: OT Standard Panel Sizes?
Date: Sun, 08 Dec 2002 03:18:44 -0000
Organization: Your Organization
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References: <email@example.com> <firstname.lastname@example.org> <3DF18783.38471AB0@mfi.net>
In article <3DF18783.38471AB0@mfi.net>, email@example.com says...
>Peter Bennett wrote:
>> On Fri, 06 Dec 2002 23:26:51 GMT, Spehro Pefhany
>> >P.S. Of course, 19" rack mount panels are standardized sizes- 17"
>> >(IIRC) wide, and heights in line with the standardized hole spacing on
>> >the rack cabinets, but I'm not sure if they have any standard
>> The 19" rack panels I buy are 19" wide - strange but true! :-)
>> The panel height is in multiples of 1.75 inches.
>> Peter Bennett, VE7CEI
> He may have meant that the chassis is 17 inches wide, behind the
That's exactly what it is. As others have alluded to, the standard vertical
increment (or "U") in a 19" panel system is 1.75". The system itself is a
typical North American abortion of weird units and rather irrational
dimensions. The 19" refers to the total width of the mounting flanges. Most
companies have standardized on the actual shelf itself being 17" wide.
When the Europeans (like Schroff) tried to come up with a standard rack
sysem, they realized that as screwy as it was, the 19" standard was too
firmly entrenched to change to something sensible. So they kept the outside
dimensions and rationalized the in-shelf dimensions, also adding defined
positions for their much more practical (than edge connectors) DIN41612 card
connectors. They also standardized on the basic PCB card sizes, and front
We can thank companies like Schroff, Vero and others for making sense out of
the 19" rack system. I remember very well 25 years ago, when I started with
a major North American telecom equipment manufacturer, wondering why
the hell every different 19" product seemed to have its own particular shelf
mechanics that were incompatible with any other. It was at that time that
Schroff was starting to make inroads here. Their stuff (and Varo's and
others later) impressed me as being designed by engineers instead of bicycle
mechanics or whatever.