Date: Wed, 1998-12-16 22:33:24 +0000 (GMT)
From: John Norris
Subject: Omnibus bars
To: Denis Howe 
X-Mailer: ANT RISCOS Marcel [ver 1.46]

I tried your on-line dictionary of computing and am impressed - it's
the first time I have seen the derivation given for bus.  I am sure you
are right in giving it as from busbar. The origin is, I am sure, from
the electricity supply industry and the meaning similar.  The busbars
were, and are, points of common connection for incoming and outgoing
cicuits. For example, in a sub-station there might be a couple of
transformers each feeding into the busbars via a circuit breaker and a
much larger number of outgoing circuits each controlled by a circuit
breaker.  Logically, the term was originally omnibus bar.  It was soon
shortened to 'busbar and survived like this for several years before
the apostrophe was dropped. Hope this is of interest.

John Norris




Date: Mon, 1999-01-11 16:55:33 +0000 (GMT)
From: John Norris
Subject: Re: Omnibus bar
To: [email protected]

John Norris:

> Logically, the term was originally omnibus bar.  It was soon
> shortened to 'busbar and survived like this for several years before
> the apostrophe was dropped.

I spent a frustrating couple of hours in the Milne library this
morning trying to find what I know I have seen before - i.e. examples
of 'busbar and omnibus bar. For most of that time I did little more
than encounter examples of bus bar and bus-bar in the 1900-1915
period.

I feel sure there are examples of omnibus bar and 'busbar in the IEE
Journal but I couldn't find any just by a simple index search on those
terms. There are few other printed reference works earlier than 1900
in the library so a long search through old contract
specs. etc. seemed inevitable. Fortunately, as I had only limited time
today, in the first spec I looked through I found an example of what I
was looking for, viz:

Crompton & Co's specification of August 1892 for the generating
station to be constructed at Hove for the Hove Electric Lighting
Co. Ltd.

" ... the switchboards to be Messrs Cromptons patent sectional
switchboard, each section consisting of a supporting standard carrying
a fusible cut out, an ampere meter and dynamo switch, a portion of an
omnibus bar divided into 2 sections with means of fixing a station
meter and connections including fusible cut outs for one or a pair of
feeder mains each of these sections to be interchangeable and to be
capable of being connected one to another so as to form a continuous
switchboard, and to be self contained so that both dynamo connections
and feeder connections can be made at the floor level."

I hope you will consider this proof enough but I will in any case
pursue it further when I am next at the museum (early Feb.) and will
e-mail again when I find anything further. I don't think there is any
chance of finding the first use of the term omnibus bar but (assuming
it had no earlier usage in the telegraph industry) it can hardly be
earlier than c.1882 and had evidently died out, in its unabbreviated
form, before c.1900

Hove was a d.c. station and busbars were probably used first in d.c.
stations. Rookes Evelyn Bell Crompton was a strong advocate of
d.c. systems in the early years of the electricity supply industry, as
well as being one of the leading promoters and manufacturers of
electricity supply equipment (generation, distribution and
utilisation). He was an educated man (Harrow!) so would have seen the
appropriateness of the term omnibus, whether applied to the carriage
of people or the distribution of electricity. So he might himself have
coined the term. However I can think of others who might also have
done so, e.g. John Hopkinson.

I hope this is of interest and that you will feel able to expand
slightly the section on the derivation of bus in your on-line
dictionary of computing.

I nearly forgot to add that all the instances I have found the first
letters of busbar, bus bar, and omnibus are in lower case; also that
to the best of my recollection the word busbar is usually pronounced
as though the 's' is almost a 'z' - it trips off the tongue more
easily that way - and that while the computer industry has abbreviated
the term to 'bus', the abbreviation used as jargon in the electricity
supply industry is 'bars', invariably preceded by the definite
article.

Regards

John Norris

X-Coding-System: iso-latin-1-unix
Date: Mon,  Mon 1999-02-01 15:04:38 (GMT)
From: John Norris 
Subject: Re: Omnibus bars
To: Denis Howe 
In-Reply-To: <[email protected]>
X-Mailer: ANT RISCOS Marcel [ver 1.46]

On Mon 1999-02-01, Denis Howe wrote:

>>> a power supply conductor running along the route of an omnibus or "tram".

>> "omnibus bar" - a connection bar 'for all' (analogous to the passenger omnibus - a conveyance 'for all')

> Thanks, I was worried about that last bit, I think I guessed.  I hate it when people do that!

I agree, but I have been guilty too. One can never know everything there is
to know about a subject and just occasionally one feels obliged to make a
little 'leap of faith' (alright, a guess based on less than 100%
understanding) and hope for charity from those who think they know better.

> Is there a connection between "omnibus" and "tram"?

I'm not a bus expert (maybe not any sort of expert) but I don't know of any
connection between the word "omnibus" and "tram", except in the sense that
both can refer to vehicles for conveying people.  I seem to remember that
the term 'omnibus' was adopted by a Frenchman to describe his horsebuses in
the early 1800s (but please don't quote me on that) while 'tram' originally
applied to a small wagon for carrying coal, limestone or whatever on an
industrial tramway and only later came to be used for a rail-borne
passenger carrying vehicle.

(Is there a connection)

 > Between tram rails and electrical bus bars?

No.

> Were trams called "omnibusses"

Not that I know of.

> or are trams red herrings?

Lovely noisy beasts with delicious graunchy noises, far, far superior to
super silent rubber tyred trolley buses (IMHO!) and running on rails, not
busbars.  Definitely better when red (L.T.) but preferably not (h)erring in
the wrong direction.

> Aren't electrical bus bars called rails too (e.g. power rail), or am I imagining that?

I can't speak with authority on this.  I do vaguely remember the term 'rail'
being used in wireless terminology (when I dabbled in radio building 30-40
years ago) and the -ve rail (or +ve in these semiconductor days) on a
circuit board is certainly a conductor for common connections.  It has
similarities with a busbar, though the connections are fixed rather than by
switches.  There may also be other busbar-like uses of the term 'power rail'
that I am unaware of.  However, the conductor rail on a railway or tramway
is quite different.  A rail, yes, and a conductor, yes, but not a busbar.
(Albeit that it may have several incoming connections from supply points
along the route and several outgoing connections in the form of trains,
it is not in any normal sense of the word a busbar.

I hope this helps.

John Norris