7-digit dialing
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.
*
10-digit dialing*
NANPA*
overlay plan*
list of country calling codes*
E.164
