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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: deploying patch cords
Date: Wed, 2 Jul 2025 20:01:02 +0100
Organization: Poppy Records
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Don Y <blockedofcourse@foo.invalid> wrote:

> On 7/2/2025 2:19 AM, Liz Tuddenham wrote:
> >> I have lots of "1-to-1" connections between network appliances.
> >> I'm trying to think of the most effective (not efficient!) way
> >> of doing so.
> >>
> >> E.g., imagine two switch-like appliances (lots of ports arranged
> >> side by side).  They have to be connected to each other.
> >>
> >> One approach is to locate them physically adjacent and use identical
> >> length cords to connect port 1 to 1, 2 to 2, 3 to 3, etc.  This works
> >> as long as 1 ALWAYS connects to 1 and never, e.g., 18!
> >>
> >> When you have more than two such devices, there are other options.
> >> E.g., imagine a set of 8.
> >>
> >> You can interleave them:  AaBbCcDd  and try tot same 1-to-1 connection.
> >> With the same caveat.
> >>
> >> Or, could create "sandwiches" where half of A goes to half of its
> >> counterpart "above" with the other half to the counterpart "below".
> >> Esp for devices with two or more rows of 8P8Cs.
> >>
> >> You could lump all of the devices of one type together and
> >> those of their counterparts:  ABCDabcd
> 
> <https://mega.nz/file/omoiWZoD#IXzd5heL6QmTIZJ5upl-RpuPDQzXODugVb9IGJzZ0RI
> >
> 
> > The 'sandwich' arrangement will be easiest for a blind person because
> > they only have to remember one linear order of the ports:
> > 
> > ABCDEFG...
> > abcdefg...
> 
> I think so.  Cables never cross so you don't have to trace a cable
> under/behind another (like in the interleaved approach).
> 
> The downside is the top row of the top device and bottom row of the bottom
> device are missing adjacent mates.
> 
> A possible solution is to build one of the devices as a "single row"
> (instead of the dual row common in switches).  This would require placing
> one above/below each row of an opposite device.  And, thus ensures the
> top and bottom devices have nearby mates.
> 
> [This seems to be a good take-away!]
> 
> > There is a risk with the 'sandwich' system that someone could plug an
> > output to another output in the same row.
> 
> I think they can be relied upon to "follow" the adjacent patch cords
> to know when they have advanced or fallen to another row.
> 
> > Another possibility would be to use a matrix with shorting plugs and no
> > connecting leads.  If it is imperative that only one-to-one connections
> > are permitted, the sockets could be break jacks to interrupt the
> > connection to all the subsequent jacks in that row or column.  (The
> > disadvantage of break jacks is that there are a lot of series contacts
> > to go faulty.)
> 
> I want to allow for the possibility -- in an unusual situation -- for
> 1 to be broken from 1 and mated to 82, instead.  E.g., if the mated 1
> malfunctions.
> 
> But, this would be a "singleton" connection that could easily stand out
> among the more orderly other connections.
> 
> The sandwich illustrated relies on lots of very short patch cords.
> This keeps things dressed nice and tidy.  But, may require care in
> their manufacture -- e.g., if you plug in one end and have only
> a few inches of service loop to ensure the other end is *oriented*
> in the correct direction.
> 
> It also means you'd need a few "exception handlers" -- longer cords
> to deal with the 1-to-82 case alluded to above.

It sounds as though your problem is very similar to the problems faced
by the designers of manual telephone switchboards a century ago.  I
would look around and see if it was possible to pick up some NOS
switchboards - or at least read up on some of the old journals: Bell
Labs, POEEJ.


-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk