Seven-digit dialing

7-digit dialing7-digit diallingseven-digit diallingfixed-length seven-digit numberseven digitseven-digit
Seven-digit dialing is a telephone dialing procedure customary in the territories of the North American Numbering Plan, for dialing telephone numbers in the local calling area.wikipedia
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North American Numbering Plan

Area codeArea codesArea code(s)
Seven-digit dialing is a telephone dialing procedure customary in the territories of the North American Numbering Plan, for dialing telephone numbers in the local calling area.
The intent was for subscribers not to have to dial an area code when making a local call or a call within their plan area, resulting in seven-digit dialing.

PEnnsylvania 6-5000

telephone number
A few of the largest cities, such as New York, used seven dial pulls ("PENnsylvania 5000" became PEN-5000 and later PEnnsylvania 6-5000, dialled PE6-5000 or 736-5000).
When seven-digit telephone numbers were first assigned in New York in 1920, the three-letter four-number (3L-4N) system had represented the number in the format PENnsylvania 5000.

Central office code protection

exchange code protectioncode protection
Central office code protection made it possible in some low density areas to use seven digits to reach areas in another area code.
Its primary purpose was initially to preserve seven-digit dialing of local calls across a common area code boundary in border communities.

Area code 202

202Area codes in Washington, D.C.
Washington, D.C. (area code 202) to adjacent areas of Maryland (area code 301) and Virginia (area code 703), discontinued on October 1, 1990 to allow assignment of a code in all three area codes.
Washington is thus one of the largest cities where seven-digit dialing is still possible.

Ten-digit dialing

10-digit dialingten-digit diallingten digits
Area code overlay plans introduced a requirement in most areas that calls must include the area code, resulting in a 10-digit dialing requirement.
After the implementation of the North American Numbering Plan, placing a local call within the caller's area code involved only seven-digit dialing.

Linked numbering scheme

linked-number area
Linked numbering scheme
A local call in this scheme, standardised for the 1951 introduction of direct-dial long distance calling, was originally dialled as a fixed-length seven-digit number and did not require an area code.

Telephone number

phone numbertelephone numbersphone numbers
Seven-digit dialing is a telephone dialing procedure customary in the territories of the North American Numbering Plan, for dialing telephone numbers in the local calling area.

Local call

local phone calls
Seven-digit dialing is a telephone dialing procedure customary in the territories of the North American Numbering Plan, for dialing telephone numbers in the local calling area.

Telephone exchange

exchangescentral officeexchange
Originally, telephone exchanges consisted of manual boards operated by switchboard operators.

Switchboard operator

telephone operatoroperatoroperators
Originally, telephone exchanges consisted of manual boards operated by switchboard operators.

Party line (telephony)

party lineparty linestelephone party line
A rural telephone number, often party line, was often up to four digits plus a letter or letter and digits to indicate which of the multiple parties on the line was desired.

New York City

New YorkNew York, New YorkNew York City, New York
A few of the largest cities, such as New York, used seven dial pulls ("PENnsylvania 5000" became PEN-5000 and later PEnnsylvania 6-5000, dialled PE6-5000 or 736-5000).

List of original NANP area codes

original area codesoriginal 86 area codesoriginal numbering plan areas
The initial 86 area codes were assigned in 1947 as routing codes for operator calls; the first cross-country Bell System direct distance dial call was made in 1951.

Bell System

BellBell Operating CompaniesBell Telephone
The initial 86 area codes were assigned in 1947 as routing codes for operator calls; the first cross-country Bell System direct distance dial call was made in 1951.

Direct distance dialing

direct dialdirect distance dialdirect distance dialling
The initial 86 area codes were assigned in 1947 as routing codes for operator calls; the first cross-country Bell System direct distance dial call was made in 1951.

Montreal

Montreal, QuebecMontréalMontreal, Canada
Numbers in 2L+4N cities (such as Montréal and Toronto) were systematically lengthened to seven digits in the 1950s, a few exchanges at a time, so that all local numbers were seven digits when direct distance dialling finally came to town.

Toronto

Toronto, OntarioToronto, ONToronto, Canada
Numbers in 2L+4N cities (such as Montréal and Toronto) were systematically lengthened to seven digits in the 1950s, a few exchanges at a time, so that all local numbers were seven digits when direct distance dialling finally came to town.

Telephone numbering plan

Area codeCalling codearea codes
Within the multinational calling area administered by the North American Numbering Plan, telephone numbers are composed of three fixed-length fields: a three-digit numbering plan area (NPA) code (area code), a three-digit (NXX) central office code, and a four-digit (XXXX) station number.

Area code 334

334
This dialing plan was incompatible with the introduction of area code 334 and area code 360, and was therefore eliminated by January 1, 1995 in the United States, and by September 1994 in Canada.

Area code 360

360360/564
This dialing plan was incompatible with the introduction of area code 334 and area code 360, and was therefore eliminated by January 1, 1995 in the United States, and by September 1994 in Canada.

Interchangeable NPA code

interchangeable NPA codes
As of 1995, with the introduction of interchangeable NPA codes, nearly all code combinations are useful as NPAs or as NXXes.

Area codes 301 and 240

301240 & 301240
Washington, D.C. (area code 202) to adjacent areas of Maryland (area code 301) and Virginia (area code 703), discontinued on October 1, 1990 to allow assignment of a code in all three area codes.

Area codes 703 and 571

703571571 & 703
Washington, D.C. (area code 202) to adjacent areas of Maryland (area code 301) and Virginia (area code 703), discontinued on October 1, 1990 to allow assignment of a code in all three area codes.

Hull, Quebec

HullHull sectorHull, QC
Hull from Ottawa before 2006, as every Ottawa-Hull local number originally was reserved in both area code 613 and 819). This was terminated on 21 October 2006 to allow assignment of a code in both 613 and 819, although five central office codes associated with the federal government were protected in 819 to allow dialing without potentially reaching non-government lines.

Ottawa

Ottawa, OntarioOttawa, ONOttawa, Ontario, Canada
Hull from Ottawa before 2006, as every Ottawa-Hull local number originally was reserved in both area code 613 and 819). This was terminated on 21 October 2006 to allow assignment of a code in both 613 and 819, although five central office codes associated with the federal government were protected in 819 to allow dialing without potentially reaching non-government lines.