7-digit dialing
From Wikipedia, the free encyclopedia
7-digit dialing is a popular term referring to the traditional convention in the United States and Canada for dialing local phone calls. It is also sometimes known as local format or network format.
Within the multi-national calling area administered by NANPA, telephone numbers are segmented into fixed-length fields:
- a 3-digit area code, indicating a large geographical (or heavily populated) area, such as a metropolitan area or a whole state (or special service, such as toll free numbers)
- a 3-digit exchange, indicating (amongst others) a city or other municipal area
- a 4-digit station number
Traditionally, calling from one area code to another, specifically for long distance calls, requires the caller to dial the trunk digit "1" before the code and number. More recently, with the increasing number and decreasing geographic size of area codes, it is possible to call a number in another area code that is not long distance, and such a call does require the area code, but not the trunk digit (initial "1").
Before the advent of overlay plans, it was universally accepted (and in some cases, required) that a call to a number in the same area code as the calling station be dialed without including the area code. As a result, the caller only has to dial the 7 digits of the exchange plus station number.
It was and is also possible to make a long distance call within the same area code; in this case the caller has to dial a "1" before the local 7-digit number. Until recently, in some cases, including the area code when dialing such a number would confuse the telephone system, and prevent the call from being connected.
This convention did not have a name until overlay plans introduced a requirement in some areas that all calls, even local, must be dialed by including the area code, i.e. 10-digit dialing.
Many modern cellular phones will automatically include the area code of the phone in the dialed number if the user only enters 7 digits. Although the caller only dials 7 digits, in this case the number dialed out to the phone network is actually 10 digits.
