TELECOM Digest OnLine - Sorted: Re: Telephone Area Codes and Prefixes

Re: Telephone Area Codes and Prefixes
8 Feb 2007 08:18:05 -0800

On Feb 7, 8:12 pm, Joe Tibiletti <> wrote:

> As to archives and comments of telephone number configurations, the prefix
> Zenith was used in the 1950's for non dial telephones in Pacific Palisades
> area of LA.

In some places "Zenith" was used for toll-free numbers dialed by the

> If one is familiar with telephone numbering issuance one can tell when a
> telephone number was issued in many cases.

One might be able to tell when the phone number was _first_ issued to
a customer, but not when the _current_ customer received the number.

Anyway, this is not necesarily true anymore, thanks to computer
switches and high volume carrier. Stuff gets reused and reassigned.

The evolution of the structure of a telephone number varied from place
to place. Without knowing individual history, it's hard to determine.

Local calling numbering depended on the size of the local and
intermediate calling areas and the situation when converted to dial.
In the smallest towns, one placed calls by name. When dial came
along, there'd be all sorts of number combinations for calls within
the town, to nearby towns, and toll calls. Even into the 1970s many
small towns continued these strange dialing arrangements. There were
various technical and administrative reasons as well as legacy for the

So you had all sorts of dial combinations, both number and letters

A look at a master railroad schedule that shows the ticket offices in
towns over a wide area will show the many different kinds of phone

When the Bell System planned Direct Distance Dialing, every telephone
subscriber had to have a unique telephone number in order to be
reached. They decided on the areacode-exchange-number (10 digit)
approach. This required a very complex conversion effort that took
place over 30 years. Often the town could continue to dial a brief
number (ie 5 digits) for local calls, but outsiders would use the full
10 digit number.

Let me note that numbering plans were dependent on the cost of
switchgear. Small towns didn't need nor want a long SxS switchtrain
to handle unnecessary digits and arrangements were made accordingly.

Also, toll billing for short and long haul calls was an issue. In
cities "message units" (still in use today) were used; calls weren't
itemized but accumulated on a meter. In some cities a cheap message
accounting system was used.

> Some challenges exist where a state line crosses through a town and two
> area codes are present and there is a need to dial across the state line
> without area code being used as is the case in Texarkana AR and TX.

In old days such users could dial merely 7 digits when crossing an
area code boundary. Nowadays it's more common to have to dial 10
digits, although the call remains a local call, even when crossing a
state and LATA boundary.

The Bell System History book 1925-1975 explains all this in detail.

[TELECOM Digest Editor's Note: Lisa, where would one obtain this
'Bell System History book' to which you refer? PAT]

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