Ten-digit Dialing - "Standard" Dialing

"Standard" Dialing

Traditionally, after the advent of area codes, the phone system allows callers to dial only the local portion of the phone number they wanted to reach, as long as the called number was in the same area code as that of the caller. For example, a person whose full national phone number was 212-555-7890 was able to call a number located at 212-555-3456 by simply dialing 555-3456. The phone system infers that the desired number was in the same area code, and connects the call accordingly. This is now known retrospectively as 7-digit dialing.

In this case, it is only necessary to dial the area code for a domestic call when the area code of the called number was different from that of the calling number. The phone system requires the caller to dial a "1" before the area code and number, to indicate to the phone system that the call will require a connection to another area, as trunk prefix.

"1" is also the country code for the North American Numbering Plan including United States and Canada, and therefore must likewise be dialed before the area code for international calls made to these countries.

Typically such calls were long distance calls. It used to be that a call to a different area code was by definition a long-distance call, but the significant growth in the number of area codes – and the shrinking of the areas they occupy – since that time has invalidated this assumption.

In Canada and some regions of the United states, dialing a "1" before an area code where the outgoing call is in the same service area results in an automated recording indicating that the call being made is local and a "1" is not necessary, even if the area codes are different. This is common in areas where overlays are being used. Phone companies have also warned that dialing "1" when it is unnecessary could result in long distance charges being made even when they otherwise would not have been charged.