----- 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. :-) Cheers, -- 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