7-digit dialing
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:
Traditionally, calling from one area code to another, specifically for long distance call
s, 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").
Traditionally to avoid number confusion, identical exchange numbers in different area codes would be assigned as far apart from each other as possible, so that callers living near a state or NPA boundary would not get two areas in different NPAs confused. This made it possible in some low-density areas to use 7-digit dialing even to reach areas in another area code.
Before the advent of overlay plan
s, 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 has to dial only the 7 digits of the exchange plus the station number.
It is 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 plan
s introduced a requirement in some areas that all calls, even local, must be dialed by including the area code, i.e. 10-digit dialing
. Traditional 7-digit dialing is still valid in those portions of the country not subject to an overlay plan
.
Many modern cellular phones
will automatically include the area code of the phone in the dialed number if the user enters only 7 digits. Although the caller dials only 7 digits, in this case, the number dialed out to the phone network is actually 10 digits.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
for dialing local
Local call
In telephony, the term local call has the following meanings:# Any call using a single switching center; that is, not traveling to another telephone network;# A call made within a local calling area as defined by the local exchange carrier;...
phone calls. It is also sometimes known as local format or network format.
Within the multi-national calling area administered by NANPA
North American Numbering Plan
The North American Numbering Plan is an integrated telephone numbering plan administered by Neustar which encompasses 24 countries and territories, including the United States and its territories, Canada, Bermuda, and 16 nations of the Caribbean...
, 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 areaMetropolitan areaThe term metropolitan area refers to a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metropolitan area usually encompasses multiple jurisdictions and municipalities: neighborhoods, townships,...
or a whole stateU.S. stateA U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
(or special service, such as toll free numbers) - a 3-digit exchangeTelephone exchangeIn the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
, 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 call
Long Distance Call
"Long Distance Call" is an episode of the American television anthology series The Twilight Zone.-Synopsis:A boy communicates with his father's European-immigrant mother, who had recently died, using a toy telephone that she gave him on his birthday before her passing. The boy, Billy, runs out in...
s, 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").
Traditionally to avoid number confusion, identical exchange numbers in different area codes would be assigned as far apart from each other as possible, so that callers living near a state or NPA boundary would not get two areas in different NPAs confused. This made it possible in some low-density areas to use 7-digit dialing even to reach areas in another area code.
Before the advent of overlay plan
Overlay plan
In telephony, especially in North America, an overlay plan is the practice of introducing a new area code by applying it onto a geographic area that is already occupied by one or more existing area codes, resulting in two area codes serving the same area.- Methodology :Prior to the introduction of...
s, 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 has to dial only the 7 digits of the exchange plus the station number.
It is 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 plan
Overlay plan
In telephony, especially in North America, an overlay plan is the practice of introducing a new area code by applying it onto a geographic area that is already occupied by one or more existing area codes, resulting in two area codes serving the same area.- Methodology :Prior to the introduction of...
s introduced a requirement in some areas that all calls, even local, must be dialed by including the area code, i.e. 10-digit dialing
10-digit dialing
In the United States and Canada, 10-digit dialing is a popular term used to refer to the practice of including the area code of a phone number when dialing...
. Traditional 7-digit dialing is still valid in those portions of the country not subject to an overlay plan
Overlay plan
In telephony, especially in North America, an overlay plan is the practice of introducing a new area code by applying it onto a geographic area that is already occupied by one or more existing area codes, resulting in two area codes serving the same area.- Methodology :Prior to the introduction of...
.
Many modern cellular phones
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
will automatically include the area code of the phone in the dialed number if the user enters only 7 digits. Although the caller dials only 7 digits, in this case, the number dialed out to the phone network is actually 10 digits.
See also
- 10-digit dialing10-digit dialingIn the United States and Canada, 10-digit dialing is a popular term used to refer to the practice of including the area code of a phone number when dialing...
- NANPANorth American Numbering PlanThe North American Numbering Plan is an integrated telephone numbering plan administered by Neustar which encompasses 24 countries and territories, including the United States and its territories, Canada, Bermuda, and 16 nations of the Caribbean...
- overlay planOverlay planIn telephony, especially in North America, an overlay plan is the practice of introducing a new area code by applying it onto a geographic area that is already occupied by one or more existing area codes, resulting in two area codes serving the same area.- Methodology :Prior to the introduction of...
- list of country calling codes
- E.164E.164E.164 is an ITU-T recommendation that defines the international public telecommunication numbering plan used in the PSTN and some other data networks. It also defines the format of telephone numbers. E.164 numbers can have a maximum of fifteen digits and are usually written with a + prefix...