[VoiceOps] Ambiguous dial plan pattern matching

Jay Ashworth jra at baylink.com
Thu Dec 6 15:14:01 EST 2012

----- Original Message -----
> On Dec 3, 2012, at 5:21 PM, "Mary Lou Carey"
> <marylou at backuptelecom.com<mailto:marylou at backuptelecom.com>> wrote:

> > Seven digit dialing is only used in areas where there is one NPA for
> > the
> > local area. Ten digit dialing is used in areas where there is an
> > overlay
> > (more than one NPA per local area) and 11 digit (1 plus) is used in
> > areas
> > where there was an area code split. The difference between a split
> > and an
> > overlay is that a split required everyone (existing and new end
> > users) to
> > change their NPA to the new area code. Overlays allow you to assign
> > numbers
> > from the new NPA to new end users but allows the existing end users
> > to keep
> > their old NPA.

Note that while it's technically possible for the switch in an overlay
area to assume the same NPA on a 7-digit dialled call as that of the
calling line, the FCC forbids this, in an attempt to make it less forbidding
to take a number in the overlay NPA: the incumbent numbers get no accidental
pioneer's preference.

In a related story, your cellphone may accept 7D numbers in it's phonebook
and dial them properly for you (unless you have Metro, who for some reason
think that's A Bad Idea), but I guarantee you you can't send SMS messages
to them unless you add the NPA in, so do. :-)

-- jra
Jay R. Ashworth                  Baylink                       jra at baylink.com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
St Petersburg FL USA               #natog                      +1 727 647 1274

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