TELECOM Digest OnLine - Sorted: Re: Historical Rules About Private Line Services?

Re: Historical Rules About Private Line Services?

Carl Navarro (
Mon, 05 Feb 2007 22:07:02 -0500

On 5 Feb 2007 07:34:17 -0800, wrote:

>> [TELECOM Digest Editor's Note: Although what you say is correct, telco
>> had very strict rules on things. For example, a pair of wires from
>> point A to point B which did not go near an 'actual phone line' but
>> was still used for communication purposes was regulated according to
>> Bell rules and defined as a 'private line' according to their
>> rules.

> Many large organizations, such as a transit system, city government,
> or large manufacturing plant, had their own private telephone
> networks. As I understand it, these networks were not
> interconnected with Bell and operated and maintained by the owner.
> In the 1960s and even 1970s you would see two phones on a desk, a
> typical Bell 500 set, and then an obviously old AE (Automatic
> Electric) phone, with a fabric cord, the metalic stripe accents on
> the handset, etc. I doubt that the owners of such systems paid Bell
> anything for them, otherwise, they would've interconnected and been
> more up to date.

> The Phila public schools had a modest PAX (private automatic exchange)
> in most schools for internal use within the school. Each classroom
> had a non-dial phone. When the handset lifted it rang in the school
> office. The school office phone had a dial. No interconnection to
> Bell. I suspect such a system required only one SxS switch and a few
> relays. I understand that system is now gone and now classroom phones
> have dials, and parents can call a teacher directly, instead of making
> the teacher come to the school office where the outside line was.
> (I'd love to know what happened to that gear when replaced.)

Sure, in a common battery office, you didn't need any moving parts :-)
A cord board had some number of cord pairs, an attendant headset, and
a rotary dial mounted on the attendant's desk. You brought the
exchange line(s) to a bank of jacks, and the box of relays to sense
the current of the phones and bring in the signal to the board. IIRC
we called them 557 cord boards and they still existed in answering
services to the mid '80's. A new-fangled company called Amtelco made
an add-in that read DID numbers to make it continue to work toward

ALL of our phones were AE's, after GTE bought us out. Before that
there were some North electric gear, like Ericofon's. I don't
remember if we had any Stromberg keys, I only remember the AE 187
mechanical stuff and early 1A1's. Toward the later days, we still had
a TON of Leich crossbar in service.

I remeber that the early PBX's had some sort of out dial restriction,
whether by tarriff or by preference. Only the attendant console could
dial outside, and all the other phones could dial internally, but had
to dial 0 to make an outside call. In fact, a Leich console had both
a dial and a keypad. The keypad dialed internal numbers and the dial

PAX Steppers only had to have a line finder, first selector, and a
connector, since the 3 digit numbering plans were easy. A first
selector only used levels 1,2,3 and maybe 9 and 0. The first levels
went to a connector, the 9 to a trunk, and the 0 to an attendant.

The last stepper I worked on in 1980 went to some third world
country. Why, I haven't a clue. More of it probably went to a guy in
New Philadelphia, OH for precious metals reclamation and landfill.

> If anyone can offer more about such large private networks used in
> industry, I would appreciate if you'd post it.

Of course the most successful private network was some railroad named
Southern Pacific. I think they went public about 1980 or so as

Carl Navarro

[TELECOM Digest Editor's Note: One of the larger private systems was
'Unitel' which was the United Airlines private network. I recall
when we discovered a seven digit local number in Elk Grove, IL termin-
ated on tne Unitel network and the type of things which could be done
on that network. Elk Grove was like the main hub of United Airlines,
and it was also the central switching center for Unitel. Imagine, an
open-ended airline private phone network without a single bit of
security on it. Quite literally, when you dialed that seven digit
number, you were answered by fresh dial tone from Unitel to do
whatever you wanted or call as you liked. Dialing '9' off of that
network was nothing much; you were limited to _very_ local calling in
Elk Grove only. The three digit codes one dialed were the main thing.
Dialing SEA (732) got you the Seattle airport centrex; dialing 673
(ORD) got you the Chicago/Ohare centrex and there were three digit
codes for almost every airport (where United traveled) in the USA
and Canada. After you dialed the appropriate three digit code, then
the mystery started all over again. From the remote dial tone in those
airport centrex systems, more three digit coded were possible to still
other places.

For example, from SEA (732), continued dialing of 263 (BOE) got you to
the centrex of Boeing Aircraft at their offices in Seattle. All of
these places allowed one to dial '9' for local calls in their
communities, or (typically) a three digit code for a WATS line,
peculiar to the community it (the network termination) was located
in. Of course, there was a 'local' WATS line (out of Elk Grove) that
one was expected to use -- not the WATS line out of LaGuardia Aiport
or Seattle, or off of Boeing Aircraft. And it just went on and on like
that; there were sort of odd loop arounds; you dialed 732 to reach the
Seattle centrex, but the people in Seattle used some other code to
reach headquarters in Elk Grove, so if you went in on 732 and (then
new dial tone) dialed the other code you would wind up back where you
started. One of the three digit codes reached the Reno, Nevada City
Hall switchboard which was weird. On that one after dialing the code
from Elk Grove, instead of a fresh dial tone, it started ringing and
after a few rings, a woman answered as 'operator'; when asked who she
was, she replied 'Reno City Hall'.

Another very strange network was/is 'Stanotel', the Standard Oil
Company network. Based out of the Chicago office, there was also a
'hub' for it in Tulsa, Oklahoma. That is to say, there were places on
the network you could not reach out of Chicago directly, but if you
used the 'tie-line' to Tulsa, then you could continue dialing out to
other places. Both Unitel and Stanotel were very unusual hybrid
systems, and I expect, quite expensive to maintain, but apparently
_less expensive_ than toll charges had the Bell System been used. PAT]

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