What is an area code “overlay”?
In an overlay, the new area code has the same geographic boundary as the existing area code. Existing phone numbers and local calling scopes don’t change, but 10-digit local dialing becomes necessary. Ten digit dialing is necessary because two different homes in the same geographic area can have the same seven digit phone number but each would have a different area code.
An NPA (or area code) overlay occurs when more than one NPA code serves the same geographic area. In an NPA overlay, code relief is provided by opening up a new NPA code within the same geographic area as the NPA(s) requiring relief. Numbers from this new NPA are assigned to new growth on a carrier neutral basis, i.e., first come, first served. Mandatory customer number changes within the affected overlay relief area are eliminated. In most cases, with the overlay relief method, 10-digit dialing is required for some of the affected customers’ calling patterns. Since the overlay relief method could result in unequal dialing for those customers served out of the overlay NPA, mandatory 10-digit dialing is recommended for all NPAs covered by the NPA coincident with the implementation of an overlay. The overlay method reduces or eliminates the need for customer number changes like those required under the split and realignment methods. It also allows the option to eliminate the permissive d
