[SBE] Rack standards

[Rod Simon]

Humm....

Similar stories different origin.  
I'd put my bet on the Railroad/ telegraph origin not Bell labs for 2
reasons:
 1) I believe it dates back to before Bell Labs
 2) The Telco equipment standard was 23" for a number of years (and still
may be).

Rod 

-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Bruce
Doerle
Sent: Friday, October 28, 2011 5:09 AM
To: sbe member discussion mail list
Subject: Re: [SBE] Rack standards

http://www.classiccmp.org/pipermail/cctech/2006-May/020764.html

On May 1, 2006, at 11:51 AM, Lyle Bickley wrote:


> Here's an interesting link on the subject. The short of it the origin 

> of 19"

> racks were as Telco switching "relay racks".

>

> http://encyclopedia.thefreedictionary.com/19%20inch%20rack


And the rest of the story (so to speak) as to _why_ 19":

I asked a fellow "middle aged" phart who (also) worked with genuine Bell
System auld pharts to verify my memory of where this came from -- it was all
a matter of convenience (and cost).

The engineering department (Bell Labs) planned equipment layouts based on a
24" grid system. To build the relay racks, channel iron 2.5" deep (measured
on the outside) was used as it was very common and relatively cheap.
24 - (2.5*2) = 19 inches for the shelf space.

The above was designed for the first relay-based telephone switches.

Mike