TELECOM Digest OnLine - Sorted: Re: Question About NXX Exchange Numbers: Are They Geographic Areas?

Re: Question About NXX Exchange Numbers: Are They Geographic Areas?

William Warren (
Tue, 08 May 2007 23:24:09 -0400

Rick Merrill wrote:

> Patrick E. Burns wrote:

>> Mr. Dykstra,

>> I happily found your on-line list of NPA/NXX's (area code plus exchanges)
>> with some geographic information attached.

>> My understanding is that telephone exchange numbers can represent
>> geographic areas, similar to a ZIP code area or census tract. Is
>> that the case?

Each NANP exchange code is associated with a Rate Center, which has a
geographic location represented by its V&H Coordinates. You may
convert from V&H to Lattitude and Longitude, but you need to do some
more research to find out how.

If you contact the current Numbering Plan Administrator, they will
sell you a list of all NPA/NXX codes and their associated Rate
Centers. From that, you may convert V&H to Lattitude and Longitude and
thus pinpoint the "location" of each NXX: Rate Centers almost never
cross state borders, and are usually associated with one town or area
of a city, so it's fine-grained enough for targeted calling within a
given geographic area.

> No. Many people have ported their number to a cell phone. When they
> move they take that number with them. Ok, that is true of some
> percentage and that may be enough for your purpose. But to tell if a
> given, single number is "somewhere" - don't count on it!

> [TELECOM Digest Editor's Note: But I think it would be fair to say
> that although local number portability is possible, not that many
> people have taken advantage of it; certainly not that far out of the
> original area of the number. Having said that, now I suppose I will
> hear about a New Yorker who took his 212 number to California or vice-
> versa, but it is still relatively rare. PAT]

The V&H coordinates of the Rate Center associated with a given exchange
show the physical location to which all calls made to that exchange are
billed. Although long distance competition has reduced rates and
sometimes caused competitors to offer flat rate service for long
distance, each call is still accounted for in the old way, i.e., it is
recorded as originating in one Rate Center and terminating in another.

And, please remember that Local Number Portability does _not_refer to
geographic movement! The "portability" is between competing ILEC and
CLEC companies which offer service to the Rate Center represented by
the NPA/NXX code, _NOT_ between Rate Centers! You may change providers
(e.g., Verizon to Comcast), but the number you port is _still_ "homed"
on its old Rate Center.

Cellular users must pay forwarding charges for calls outside their
Rate Center: their carrier may choose to bundle those charges in with
their basic service or make any number of other price concessions, but
the number _always_ stays at its associated Rate Center. That means
that no matter where the cellular user is located, calls made to
his/her cell phone _always_ go to the terminating Rate Center first,
and are then forwarded within the cellular provider's network to a
cell tower that serves the user's current geographic location.

As far as the originating office is aware, the call stopped at the
terminating Rate Center, and it is recorded that way.



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